Several Problems with BL2 and TPS

Ok, I really don’t know what to do anymore. My System:

AMD FX-6100 Six-Core, 3.30 GHz
16 GB Ram
Geforce GTX 770
Windows 7 64bit

While the GPU might not be the newest, this should easily be enough to run BL2 and TPS on minimum without any problems. I mean, it ran freaking Arkham Knight on release without much trouble.

Ok, lets get started:
General low FPS: 25 maximum, settings don’t change anything here, besides PhysiX ofc. Not much to say.
Slow loading time: about a minute until the game opens, about 30 secs checking DLC, about a minute to load a map.
Short freezes when saving, swapping charakter, choosing difficulty, or going into/leaving FFYL.
Graphic issues when using elemental guns: slag weapons don’t shoot bullets, but huge pink cubes which make aiming absolutly impossible.
Delayed inputs, especially in menus like the inventory or using scopes. Fighting flying enemies, especially mobile ones like gyrocopters, is more or less impossible.
Laserweapons spawn their projectile so far away, its literary impossible to hit anything in meleecombat. Not sure if thats a bug or a feature.
The mortarcircles during the Slabking mission don’t show up, the hole section is basically run and pray.
In TPS items often fall through the ground, but that might be a common problem.
Rockets from launchers often explode instantly.

Those are the things I can think of right now.

What I allready tried:
Reinstalling to another directory
Reinstalling to another hard drive
Reinstalling my hole system
Uninstalling PhysiX
Swapping out my GPU
Swapping out my ram
Tweaking the .ini
Compatibily mode

Drivers are up to date. These two games are the only ones that pose such a problem. Games like Arkham Knight, Far Cry 3/4, Skyrim and Hitman 6 run without problems. Does anyone have an idea here?