[GAMEPLAY] Low FPS and Constant HUD Flickering in Full-Screen Mode

This started back after a certain patch in 6.0. I don't specifically remember which one. I used to get 100-120 fps easily. Ever since that patch, It's dropped down to a constant 50-70 fps, rarely going up to 80-90 and then dropping fps again back to 50-60. I get drops during fights too. Everything is going fine, and then 1 moment in the team fight my fps drops to like 01, 08, etc. I have everything turned off that can be, and all graphics on lowest already.

The even bigger issue is the HUD flickering. I can't have my game in full-screen mode, because if I do, the HUD constantly flickers black, like every 0.1 seconds. it's very very very distracting. I've tried reinstalling, I've tried Repair Tool, I've tried compatibility mode, I've tried "Repair" in the client options. Nothing seems to work.