Bathtub faucet stem seat is frozen and won't turn.
First off WD-40 is worthless as a penetrate. get some PB blaster or Kroil,,they are MUCH better!!! Take something larger than the hex,smaller than the threads and tap a bit on them,,,hard enough to rattle the threads,not hard enough to force them thru the threads. Some of those are stuck so tight you HAVE to buy a new faucet. Try putting a longer cheater wrench on end of allen wrench for a little more leverage,,,but not so much you break whole faucet from its moorings!! Then tap on that,,,sometimes it takes a little vibration to kick things loose.