[Muddog]

I don't know pucky about these Re Gen2 buggies and I didn't stay at a Holiday Inn last nite, but here's my thoughts. Something don't sound right . If you are only getting 10 MPH, you must be on code 1( did these carts have speed codes) or have low battery voltage. At code 1 you should have plenty of torque, I would think you would have no loss of speed on hills on code 1 unless something's not right with your cart. Check your pack voltage 12 hours after charge and make sure you have good voltage. That's all I can give you on that, maybe some of the pros will tell you whether I am right or wrong.

Yes, a controller is the best first upgrade along with at least 4 awg cables and a heavy duty solenoid to go along with it. By feeding your motor more amps you will gain torque.
I put a 500 amp Curtis thinking the same as you, that I'll cook my motor. We'll so far it has drug logs out of our hurricaned yard and pulled a locked up lawn tractor across 2 yards and a paved road, leaving ruts in the yards and black marks on the road. My motor is still going strong.
Make sure everything's right with your buggie first. A controller upgrade will do you no good unless all is right. And I don't think all is right