Mouse Acceleration cannot be disabled in Mass Effect 2

Hi!

I started playing Mass Effect 2 recently and noticed any time I right-clicked and zoomed in with a weapon, afterwards my mouse would suddenly have a ridiculously high sensitivity. I turned the mouse sensitivity down on my mouse, disabled the mouse programme, and in the ini file I disabled mouse smoothing, vsync, mouse dampening, lowered base sensitivity to really low etc. I have done every little thing that has been recommended by various people online and I still have mouse acceleration every time I right click and aim with a weapon.
But, if I right click to aim at an enemy when using biotic powers then come out of that little pause screen, it doesn't affect my sensitivity.

I cannot switch to controller to fix this issue as standard controllers cause my hands to seize up so please don't recommend that as a solution for me, I'd do it if I could but I can't.

I'm not sure what else to do to fix this, I've had to lower the game difficulty to the easiest possible because I can't aim, keep missing and running out of ammo when I'm in battle haha.