Trailer brakes are supposed to complement the TV braking and not be the primary
braking. If you are running on P3 - then this is the most aggressive setting;
You probably feel the trailer braking before the TV brakes take a bite;
It's a balance finding that sweet spot; Try backing off and use P2 - and then
lower the gain SLIGHTLY; If you can smell the TT brakes and they are getting
hot then they are losing efficiency and you are relying more on the TV brakes.
On steep hills, slow down....... there's no shame in going down a hill at 20mph
instead of 30 mph !!! as long as you do it safely;