FPS

Lower your graphics settings.
If you've tried basically everything -- just disabling a lot of addons can help you gain hella FPS.
It just so happens that there's a really bad relationship between addons and how well your game performs. The fewer addons you and a server have, the better your FPS and other things as well.
If you can't remove plugins and addons... Then sadly, the only thing that you can do is physically upgrade hardware.