I would think the top strut bearing could be affecting it, but that may only explain the erratic shaking. The strut rod bushings are probably worn out - you said you checked these, but it can take a lot of force to notice that they're shot. These bushings (called cone bushings) are pretty cheap- I'd replace them to rule it out. Again, this may explain the shakes but not necessarily the other things. The erratic pulling could certainly be due to these bushings.
It is possible the check valve for the booster is failed- boosters don't really fail that often but the check valve could go bad. It works harder on a turbo too.
The hard pedal combined with a pull sounds like a stuck caliper. Were you able to replace the pads properly with the recent brake work? Usually new pads cannot be inserted into a stuck caliper- the pistons won't move back far enough.
I'd say the front calipers need closer attention- something's not right with them. COuld be just pads not sliding correctly. Some brake grease may fix the whole problem. Recently I saw calipers (rears) where the pad retainer had been bent up and was stickign out of the caliper- surely that was not doing its job correctly. So strange things can happen. Do a thorough visual check of the parts again.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 221K, 88 744GLE- 202K, 91 244 181K, 88 244GL 145K