According to the the schematic I have access to, the radio, heater/ac control assembly, and interior wiring system and the engine control systems run along the same trunk line to the fuse block. Your seat motor is drawing more amperage than it should and is affecting the other circuits. I know that this sounds rediculous but let me share one with you.
Years ago I had a 63 Chevy II. The brake lights blew a fuse while I was out driving. I had no spare so I took the fuse out of the wipers ( not raining ) which was of a higher amp rating. When I inserted it into the fuse block, the engine started cranking over. You wold not think they were related either!
You just might want to get another seat motor or check the wiring to the seat and see if it is pinched in the mechanism or shorting out under the carpet somewhere.