Be careful, very strange the heater worked on the one at a time test with 5A jumper. but thru switch with 5A jumper it blew fuse.
Was the heater wire hooked to a separate switch terminal; or same terminal as the other outs?
It could be as you say, the old motor, if bad bearings/bushing or fan blade interference, it will put a drag on the motor and draw more amps possibly. This would be an intermittent happening. So we will ignore that for today.
