Umm, why are you afraid of a shared bus? It is only one additional stop before you are on your way. Even POFQ sometimes shares buses with POR. It isn't a big deal, IMO.
I have never tried it, but I don't see why your plan to walk to the TTC wouldn't work. If you are staying in the Poly villas, it might be just as close as the Poly bus stop. As far as I know all WDW buses run about every 15-20 minutes, at least as a general rule. In practice, the schedule can get messed up, but that is the plan, I believe.
Hopefully, someone with more certain knowledge about this will be able to answer your questions.
However, don't worry about it. The buses are generally just fine. An occasional glitch can happen anywhere, even (gasp!) POFQ!
Good luck