Hey Reed
Sometimes a new belt will be tight (it will also squeal a little). Some people break a belt in by running it for 30 miles at lower rpms. Check to ensure that you don’t have left over pieces of the belt in your clutches. I doubt it’s the track tension, because you didn’t say you recently changed it. If you keep blowing belts it’s because your clutching is wrong (new elevation?) or it’s time for them to be rebuilt. You can also check a few other things. Take off the belt, get the track off the ground and spin the clutches (to see if you have a bigger issue).
See your owner’s manual, but here is a quicker over to check your track tension. Get the track off the ground. About halfway on the rails, push down on each side of the track (2.5lbs of pressure). I think you should have about 2” of slack. Measure you tension bolts if you need to changer your slack (some say run it till it ratchets and back off for the powered). Also they say to rev up the track, when lifted, and see it you have any right to left movement, if so make minor adjustments.
As for not moving up hill when parked, don’t park up hill (to really say, I would need a better description of the conditions. Hope this helped : )