1. HTTPS requires all resources to be loaded over HTTP on the page. If I check a thread then I notice that your signature has a picture in it that loads over HTTP.
2. Your headinclude template still has a variable that's pointing to HTTP: "var AJAXBASEURL = "http://lf3performance.com/";". The AJAXBASEURL is used to load CKEDITOR if I recall correctly. If this is a bug in vBulletin then just manually change it in the template.
3. This plugin is recommended:
https://vborg.vbsupport.ru/showthread.php?t=288060