As for your fluid, you need to measure it out. I did the same thing when I first changed mind then blew diff fluid everywhere through the breather. The rear is 400ml and the front is 330ml
I’ve had some issues with burning belts but I also have 32s. Just got a gates and we’ll see what it does. The clutch kit seemed to help a little. Some of mine is the type of riding I do, but honesty, I never had issues with my old Rzr with the same abuse. I’m hoping the new gates belt will grip a little better.
I don’t know about the brakes but harbor freight sells a decent brake bleeder that’ll suck the air right out of the lines if that’s the problem.