Hey new fella, welcome to our world!
Tape chewing on this is almost certain to be a problem with the sleeve on the capstan, which was originally made of a latex-based rubber that becomes liquid with age and constant heating/cooling as the deck is run. R/C model shops sell the far superior silicon pipe that replaces this, I/D is 0.037", O/D is 0.19" but the O/D isn't critical as it's the capstan to pinch roller dimension that dictates the speed, the sleeve is further back on the capstan and simply pulls the reel that takes the tape from the full side during play.
Drive from that capstan to the takeup spool is by another rubber - the idler tyre - which runs against the sleeve, that tyre is sometimes found to be suffering the same thing but often, removing from the rim and cleaning the tyre with IPA (to clean off the molten rubber from the tyre that it would pick up from the liquifying sleeve) followed by a soak in glycerin (to soften and preserve the tyre and prevent its going the same way as the old sleeve) will be all that the tyre wants. If that [tyre] is also decomposing, then genuine, N/O/S ones are available for Sharps or you can use a suitable nitrile O-ring which, although they have a round profile, will work just as well.
Looking at the manual on the UKVR data DVD, later 8585s had a slightly different takeup arrangement in which the capstan runs directly on the idler tyre, if yours is that type then follow the above regarding the tyre but ignore the bits that involve the sleeve.
Your switch issue is probably caused by nothing more serious than poor contacts, so a scoosh of contact spray
(There's no Servisol S10 in the USA "officially" so you'll have to make do with Deoxit) into the switch followed by a few flicks back and forth will take care of any glazed or corroded surfaces.