Wow. Never heard of a self-frying fish before.
Can you lift the heater off the bottom of the tank or run it diagonally? Then, he couldn't lay against it.
You could shield him from the heater by a very heavily perforated piece of PVC pipe.
Make it about 1"+ in diameter bigger than the heater so it can slip inside. Will need lots of 1/2" holes to keep good flow around the heater.
Possibly cover the PVC with mesh if fish that can get inside the pipe are in the tank.