I have the exact same type (85 325e). Ive had some problems with the power windows before. At one point I just yanked the buttons out of the car and cleaned them with some WD40 and/or alcohol.
If that doesnt work try replacing fuses, I have yet to find a place that sells 7.5 amp fuses without being in a huge set and 7.5 seems to be the ones that burn out the most often. I replaced them with 5 amp, theyll burn out faster but its better to have them burn out with a 5 than mess stuff up with a 10.
I dont know much about the steering res but it shouldnt be a big problem to find the proper fluid. Also you mentioned it being quiet, mine can sound fairly loud at higher RPMs, I have a stock muffler but maybe a leak or two in the headers. I like the sound my 325e makes