Lohanimal,
Here are my thoughts:
(1) Choose tonearm to match cartridge. Just about any tonearm will work on the TTS8000, except before purchasing a 12-incher you might check to be sure it fits the armboard.
(2) See my response to (1)
(3) Wood vs slate vs Panzerholz (which is a kind of wood, after all). These materials can all give excellent results if the plinth is otherwise properly designed and engineered. I personally have found that a combo of slate and a hardwood (cherry, not Panzerholz) is the most neutral I've ever heard, but in fairness, I have never "heard" a Panzerholz plinth.