First off, thank you very much for that detailed response! I'll do my best to respond to everything.
I haven't taken the center console apart yet, so I don't know if there's a bunch of crap down there, but I wouldn't be surprised. When I bought the car, the "ABS Off" light was on as soon as you started it. I took it to the Audi dealership and they replaced a fuse or relay and that shut it off... until you start it up and drive several hundred feet or up to around 20 mph usually.
The power steering issue is separate from the ABS issue as far as I can tell. I had a leak in the high pressure line, so I took it to a hose shop and had it fixed (as detailed above) and reinstalled it. After that, there was no power steering assist. Before I replaced the line, it was intermittent. Going around a corner, like say a left turn at a light, I would maybe have assist at the beginning, then lose it halfway through, and regain it at the end of the same turn. It was mostly random, but may have been related to braking or something.
When we cracked the line after installing the hose, the car was running and only a trickle came out. No spewing or anything. I'm pretty sure the pump needs replaced. Sounds to me like it was going out before and the air we left in that hose line when we reattached it finished it off.
Thanks for the insight on the electrical problem. In the video when I was outside the car and the lights were off, I probably could have gotten in it and started it, but I was messing with the door locks because sometimes it would be fine unlocked and then the lights would be on again as soon as you locked it. When I turn the ignition at the beginning of that segment and the lights come on, they soon turn off. As soon as they turned off, I would have probably been able to start the car. I just wanted it to turn the lights on by locking and unlocking so there was some video of what was going on. It didn't really cooperate. Haha
Also, thanks for the heads up on that manual. I have checked it out on Amazon a couple of times, but it's been out of stock each time. If I can find one, I'd like to buy it, but money is also somewhat tight (college student) and if I can fix my problem by looking at a Chilton manual for free, then I'd rather do that. When I can though, I'll get the bentley manual.
And yeah, it does sound like you lucked out on your Audi! You should put some pictures up. You can also register your Audi on this site: 1991 Audi 90 Quattro 20V at http://registry.audi20v.net
(that's my Audi that it links you to). I'm not sure it does much, but it's nice to see other people's Audis.
Thanks for the reply again! Hope to see you on the forums in the future.