Re: Microphonic pickup
I wouldn't pot a pickup unless there weren't any other options. I fixed the feedback problems my Gibson 490 pickup was having when I flipped it's magnet to do the Peter Green trick. I put a single layer of vinyl type electric tape over the long edge of the bobbins, and as I recall, over the center. Put the cover back on, and it went from having out of control feedback problems, to being just microphonic enough.
Could be a number of different kinds of vibrations causing feedback though, and the problem could even be related to how the pickup is mounted.
Pete