Well scratch the boot replacement...
The axle joints are bad...Tested them from Kent's mercedes source videos and they bind badly on both ends. Might explain the popping noise from the rear when I turn over bumps which I thought was (and I will be replacing throughout this work since I have the parts) the carrier arm bushing.
Heres a video of the binding:
https://youtu.be/liRLcNWQ-fE (once it finished uploading).
EDIT: Also explains why I couldn't get it out of the hub before -- It probably binded up without the car being at ride height and wouldn't allow the spider joint to move in/out.
Whats the best action from here? The prices look steep...