The front drive shaft is plenty long and shouldn't cause future problems. To be sure, remove the rear shaft and see if your vibes are gone, if they are you are golden up front.
If a wheel will fit a 10.5" wide tire it will also fit a 12.5" wide tire, but that is not necessarily true the other way around. If the wheel is 10" wide it will fit a 12.5" wide tire but I wouldn't recommend putting a 10.5" wide tire on it.
Mine works. I think I take it out of 19 and put it in 20. I think those are the numbers anyway. And BTW, I can start it without the clutch in and in any TC position.