I posted this link in your introduction thread:
It sounds like you may have a hub stuck engaged while the other side is free, causing the constant pull. I say that because that would make the front differential rotate in 2wd, causing the shake. I suspect that your shake is from a seized up u-joint on that same side's front axle shaft. The U-joint close to the tire is prone to that from dis-use. That's about the only explanantion I can come up with based on your description of the steering wheel shake at low speed.
The way to check is to jackstand the front end and spin the tires by hand, watching what happens. Your front axles from the diff to the hub should NOT be turning and I suspect you will find the right one is turning. I also suspect your right front hub's bearings are shot.