Use a hand impact wrench with allen bit
Use a hand impact wrench with a good allen bit(or even better a torx bit as Rev C suggests).Stuff some foil in the "allen hole" to kinda get it tight again first..A torx bit on the hand impact sounds like a great idea!!
The tap, tap tap with a hammer is a good idea also.Get some oil in there-the threads- also-try not to get it where your allen will fit.
Take your time,Luck!
Charlie