Making Margins 1 inch all the way around
Remove the line
\usepackage{fullpage}Remove all the lines modifying the margins (in 6. in your question).
Add the lines
\usepackage[margin=1in]{geometry} \pagestyle{empty}Globally replace
7.0inwith\linewidth.Replace
\begin{minipage}{\textwidth}with\begin{minipage}{\dimexpr\textwidth-2\fboxsep}(thanks to Max for catching this.)Recompile.
Some explanation
The fullpage package is a rather old package to set margins to either 1" or 1.5", plus a couple of other settings to do with pagestyles. The option [empty] sets the document page style to empty (i.e., no page numbers). Since geometry is a much more general package, it makes sense to use it instead. We therefore have to add an explicit \pagestyle command to mimic the fullpage option.
The template you're copying also added manual corrections to the margins to make the margins .5", which kind of defeats the purpose of using fullpage in the first place.
It then hard coded values for tabular constructs in the document to the width of the text assuming the .5" margins. By changing this hard coded value to \linewidth you make the tabluars adjust independent of the margin settings.
Max's suggestion changes one other setting to make sure that the \resheading command doesn't produce an overfull box, i.e., exceed the actual text width.
Here's a full example:
\documentclass[letterpaper,10pt]{article}
%-----------------------------------------------------------
% Delete this line
%\usepackage[empty]{fullpage}
% Add these lines:
\usepackage[margin=1in]{geometry}
\pagestyle{empty}
\usepackage{color}
\definecolor{mygrey}{gray}{0.80}
\raggedbottom
\raggedright
\setlength{\tabcolsep}{0in}
% Delete these lines
% Adjust margins to 0.5in on all sides
%\addtolength{\oddsidemargin}{-0.5in}
%\addtolength{\evensidemargin}{-0.5in}
%\addtolength{\textwidth}{1.0in}
%\addtolength{\topmargin}{-0.5in}
%\addtolength{\textheight}{1.0in}
%-----------------------------------------------------------
%Custom commands
\newcommand{\resitem}[1]{\item #1 \vspace{-2pt}}
\newcommand{\resheading}[1]{{\large \colorbox{mygrey}
{\begin{minipage}{\dimexpr\textwidth-2\fboxsep}{\textbf{#1 \vphantom{p\^{E}}}}\end{minipage}}}}
\newcommand{\ressubheading}[4]{
\begin{tabular*}{\linewidth}{l@{\extracolsep{\fill}}r}
\textbf{#1} & \textit{#4} \\
\end{tabular*}\vspace{-6pt}}
\newcommand{\ressubheadinged}[4]{
\begin{tabular*}{\linewidth}{l@{\extracolsep{\fill}}r}
\textbf{#1} & #2 \\
\textit{#3} & \textit{#4}\\
\end{tabular*}\vspace{-6pt}}
%-----------------------------------------------------------
\begin{document}
\begin{tabular*}{7.5in}{l@{\extracolsep{\fill}}r}
\textbf{\large Bob Mars}\\
888.888.8888\\
[email protected]
\end{tabular*}
\\
\vspace{0.1in}
\resheading{Education}
\begin{itemize}
\item
\ressubheading{University}{}{}{September 2000 - June 2004}
\begin{itemize}
\item B.S., Engineering
\end{itemize}
\end{itemize}
\resheading{Work Experience}
\begin{itemize}
\item
\ressubheading{Company 1}{Seattle, WA}{Engineer}{Engineer, June
2016 - Present}
\begin{itemize}
\item Engineer for Company 1
\item Did engineering work for Company 1.
\item Investigated different things. Overall, a great experience
that I truly valued and enjoyed. The projects I worked on were
my favorites.
\end{itemize}
\item
\ressubheading{Company 2}{Seattle,WA}{Engineer}{June 2014- June
2015}
\begin{itemize}
\item Worked on various projects
\item Used various programs. The programs I used were difficult
to learn at first but I soon adapted and things came more
naturally to me.
\item Received high marks for all my work. My work was
collaborative and highly enjoyable. The best experience of my
life.
\item Worked for several years. A rigorous and difficult, but
pleasant experience. Overall, the best experience of my life.
Highly enjoyed.
\item Employee of the month twice. Both were my highest-achieving
awards during the job. Truly enjoyed the entire experience.
\end{itemize}
\item
\ressubheading{Company 3}{Seattle,WA}{Engineer}{Engineer, June
2012- June 2014}
\begin{itemize}
\item Engineer for Company 3 for over two years. A rigorous but
pleasant experience.
\item Worked on 3 projects. All three projects were nuanced but
highly interesting in their own right. A wonderful experience
that I truly enjoyed.
\item Used various programs. The programs I used were difficult
to learn at first but I soon adapted and things came more
naturally to me.
\item Discovered important relationships between various things.
\item Worked for several years on various projects. A rigorous,
but pleasant experience. Overall, the best experience of my life.
\item Figured out things nicely.
\item Promoted twice.
\item won award.
\end{itemize}
\item
\ressubheading{Company 4}{Seattle,WA}{Engineer}{Engineer, June
2010-June 2012}
\begin{itemize}
\item{Engineer for Company 4.}
\item{Awarded best employee twice.}
\item{Used various programs. Was a great experience, that I
valued greatly. Company 4 is a great company to work for. I love
the projects that I worked on.}
\item{Won awards for my work. Worked on various projects with
various people. Overall, a great experience that I truly valued
and appreciated. }
\item{A pleasant experience.}
\end{itemize}
\end{itemize}
\resheading{Volunteer}
\begin{itemize}
\item
\ressubheading{Organization 1}{Seattle,WA}{Volunteer}{June 2016}
\begin{itemize}
\item{Recycled and helped the community in organization 1 on many
things. Was a great experience that I really enjoyed. }
\item{Worked for over two years in the same organization. We did
many things including beach cleanups, recycling events, various
events for the community.}
\item{Set up various events for the community and played a huge
role in leading this organization. Had several leadership
positions}.
\end{itemize}
\item
\ressubheading{Organization 2}{Seattle, WA}{Volunteer}{June 2015}
\begin{itemize}
\item{Worked for this organization for over 3 years. We cleaned
up trash in the community and hosted several events.}
\item{A great experience. Some of the best memories of my life
occurred while volunteering for this organization.}
\end{itemize}
\end{itemize}
\end{document}
I modified the template. Does it produce what you want?
\documentclass[letterpaper,10pt]{article}
%-----------------------------------------------------------
\usepackage[empty]{fullpage}
\usepackage{color}
\definecolor{mygrey}{gray}{0.80}
\raggedbottom
\raggedright
\setlength{\tabcolsep}{0in}
\usepackage[margin = 1in]{geometry}
%-----------------------------------------------------------
%Custom commands
\newcommand{\resitem}[1]{\item #1 \vspace{-2pt}}
\newcommand{\resheading}[1]{{\large \colorbox{mygrey}
{\begin{minipage}{\dimexpr\linewidth-2\fboxsep}{\textbf{#1 \vphantom{p\^{E}}}}\end{minipage}}}}
\newcommand{\ressubheading}[4]{%
\begin{tabular*}{\linewidth}{l@{\extracolsep{\fill}}r}
\textbf{#1} & \textit{#4} \\
\end{tabular*}\vspace{-6pt}}
\newcommand{\ressubheadinged}[4]{
\begin{tabular*}{l\linewidth}{l@{\extracolsep{\fill}}r}
\textbf{#1} & #2 \\
\textit{#3} & \textit{#4}\\
\end{tabular*}\vspace{-6pt}}
%-----------------------------------------------------------
\begin{document}
\noindent
\begin{tabular*}{\textwidth}{l@{\extracolsep{\fill}}r}
\textbf{\large Bob Mars}\\
888.888.8888\\
[email protected]
\end{tabular*}
\\
\vspace{0.1in}
\resheading{Education}
\begin{itemize}
\item
\ressubheading{University}{}{}{September 2000 - June 2004}
\begin{itemize}
\item B.S., Engineering
\end{itemize}
\end{itemize}
\resheading{Work Experience}
\begin{itemize}
\item
\ressubheading{Company 1}{Seattle, WA}{Engineer}{Engineer, June
2016 - Present}
\begin{itemize}
\item Engineer for Company 1
\item Did engineering work for Company 1.
\item Investigated different things. Overall, a great experience
that I truly valued and enjoyed. The projects I worked on were
my favorites.
\end{itemize}
\item
\ressubheading{Company 2}{Seattle,WA}{Engineer}{June 2014- June
2015}
\begin{itemize}
\item Worked on various projects
\item Used various programs. The programs I used were difficult
to learn at first but I soon adapted and things came more
naturally to me.
\item Received high marks for all my work. My work was
collaborative and highly enjoyable. The best experience of my
life.
\item Worked for several years. A rigorous and difficult, but
pleasant experience. Overall, the best experience of my life.
Highly enjoyed.
\item Employee of the month twice. Both were my highest-achieving
awards during the job. Truly enjoyed the entire experience.
\end{itemize}
\item
\ressubheading{Company 3}{Seattle,WA}{Engineer}{Engineer, June
2012- June 2014}
\begin{itemize}
\item Engineer for Company 3 for over two years. A rigorous but
pleasant experience.
\item Worked on 3 projects. All three projects were nuanced but
highly interesting in their own right. A wonderful experience
that I truly enjoyed.
\item Used various programs. The programs I used were difficult
to learn at first but I soon adapted and things came more
naturally to me.
\item Discovered important relationships between various things.
\item Worked for several years on various projects. A rigorous,
but pleasant experience. Overall, the best experience of my life.
\item Figured out things nicely.
\item Promoted twice.
\item won award.
\end{itemize}
\item
\ressubheading{Company 4}{Seattle,WA}{Engineer}{Engineer, June
2010-June 2012}
\begin{itemize}
\item{Engineer for Company 4.}
\item{Awarded best employee twice.}
\item{Used various programs. Was a great experience, that I
valued greatly. Company 4 is a great company to work for. I love
the projects that I worked on.}
\item{Won awards for my work. Worked on various projects with
various people. Overall, a great experience that I truly valued
and appreciated. }
\item{A pleasant experience.}
\end{itemize}
\end{itemize}
\resheading{Volunteer}
\begin{itemize}
\item
\ressubheading{Organization 1}{Seattle,WA}{Volunteer}{June 2016}
\begin{itemize}
\item{Recycled and helped the community in organization 1 on many
things. Was a great experience that I really enjoyed. }
\item{Worked for over two years in the same organization. We did
many things including beach cleanups, recycling events, various
events for the community.}
\item{Set up various events for the community and played a huge
role in leading this organization. Had several leadership
positions}.
\end{itemize}
\item
\ressubheading{Organization 2}{Seattle, WA}{Volunteer}{June 2015}
\begin{itemize}
\item{Worked for this organization for over 3 years. We cleaned
up trash in the community and hosted several events.}
\item{A great experience. Some of the best memories of my life
occurred while volunteering for this organization.}
\end{itemize}
\end{itemize}
\end{document}
