In regards to the e-brake:
There is an adjustor on the cable. Very easy to do (so long as it is not frozen).
Presuming the mechanism is otherwise ok at the wheels, that may fix your problem. Worked for me!
The e-brake pads can also be adjusted for wear.
If you use the cable adjustment method, you may need to slacken the cable again the next time you service the brakes.
In regards to the squeal:
If I am reading your post correctly, and the squeal goes away when you brake, it may simply be a case of common 'brake squeal'.
Anti-squeal paste on the pad backs may fix you up.
A rear bearing might squeal, though a low 'roar' is more common in the early stages. Also, the noise would likely change in sweeping turns of one direction or another. Look for cupping on the tire treads.
1986 300E 5-Speed 240k mi.