Don't bother re-pitching it of course.
Yes, 1.018 is likely high for a hefe (think I would shoot for 1.010 or 1.012) but ofter extract will do that (not attenuate as well). Unsure what your "alcohol booster" even is (sugar?)--I avoid those things. However if it just tastes a "little" sweet before kegging it will be fine after its carbonated, that really makes a difference.
That yeast and malt combo are known to go high-order so always use a blow off tube with them!
Good job fermenting the hefe yeast in the mid 60s instead of at 70+ like many do! I am a yeast freak, so I am not sure that a 1 quart starter on a single yeast pack is ever "OK" with me, but its probably fine for that beer...the only thing I would say next time is let it warm to 70+ only when it is almost completely done fermenting (to let the yeast pick up their activity and finish up). A beer and yeast like that should likley never take more than a week to be done fermenting.