I'm having this exact problem as well. I have fixed the HTTPS login loop issue with sslproxy=1 in the config and commenting out the section in setuplib.php.
My login page displays as HTTPS just fine but other random pages within moodle are displayed as HTTPS even though the entire site is set to HTTP.
If you go to site administration -> users -> accounts -> browse list of users and type in any name in the search field. When you hit submit Moodle redirects you to a HTTPS page and breaks the theme on certain browsers (chrome).
Chrome will not display non secure items on a "secure" page resulting in the theme being completely broken down (seen below).
I have yet to find a fix to this problem aside from setting the entire site to HTTPS.
Has anyone else found a solution or ran into this problem?