Lots of confusion here...
Accessory belt
Tensioner keeps breaking
Power steering pump is locked up.
Sc belt is not coming off.
Thats where we are currently.
Your accessories are spinning at the same speed as stock regardless of sc pulley size or ATI lower, and run from the crank on their own pulley. A chop off the throttle should not effect that belt.
1. A bad tensioner is ruled out, since 2nd time
2. PS pump is locked up, was it going bad and dragging on the belt?
3. Belt is routed correctly and you had it in the grooves on every pulley?
This is not a common problem on modded hellcats.....