Hi cswilsn2k,
The proxy URL in the error log is a static file URL. If it redirects then the cause is likely to be found in the web server configuration or potentially a (security) plugin that modifies .htaccess (Mod Rewrite).
Regarding Font Awesome, when a CSS file contains relative links (to fonts or images) then they would break when the CSS is loaded from the proxy location. To solve the issue it would be possible to place the Font Awesome CSS locally and convert the relative paths to absolute paths within the WordPress installation or on a custom CDN.
We usually place Font Awesome in a conditional Critical CSS entry with the option “Prepend to any” with just the specific fonts that are used. You could save up to 80% of the CSS that way.
The option Prepend to any causes the font CSS to be included before other Critical CSS on a page so that rendering of the critical CSS that uses the fonts is smooth.