My random guess is check fuses and check battery. I didn't read that you tested the battery...the first place you start, imho, for anything electric.
Disconnecting is a good start and measure voltage off and on and report back...it may be you just need a long drive to charge up a very low battery, which might be real low for a long time and because of that, the alternator is getting tired also...start with electrical basics and work up and out from there.
I'm so depressed. No one wants to come see me. :(
Mangofy your E46!