XeLaTeX Quiet Output and Halt on Error

If you want to get rid of ALL warnings you can load the silence package

\usepackage{silence}

and then issue the command

\WarningsOff*

Have a look at its documentation for selective warnings filtering and errors filtering, if you need it.

Just remember that warnings are what they are supposed to be: they warn you about something wrong in your document.

---

For your latter request, if you want xelatex to halt on errors (and exit) add --halt-on-error to the command line, otherwise, if you want a prompt where to decide what to do, add --interaction=errorstopmode to the command line.