1) front - no, center - viscous coupler or clutches, depending on manual/auto, rear - doesn't look like it.
2) Doubt it.
3) Most likely the flywheel is tweaked, replace it.
4) That's what, about 170k miles? Do you know the maintenance history? Has the timing belt been changed? If not, do it. Check all of your fluids and flush those that don't look good. Check your brakes, check for leaks and fix.