how do I set height of container DIV to 100% of window height?

You can net set it to view height

html, body
{
    height: 100vh;
}

Add this to your css:

html, body {
    height:100%;
}

If you say height:100%, you mean '100% of the parent element'. If the parent element has no specified height, nothing will happen. You only set 100% on body, but you also need to add it to html.