Yes, these things are V awkward to get out, and replacing them satisfactorily isn't much better! Loctite do a viscous grade that's good for sealing and holding these plugs, Loctite 577, it has good gap-filling properties and won't run out into places you don't want it to. Most times I seem to find that when you're fitting it, the plug wants to be screwed in too deep, and the viscous Loctite holds it where you put it really hard once it's set. I have tried pressure testing the oilway, and this stuff has always sealed wwith no leaks. Get the plug out by first heating the crank to 150C.
I have got plugs out by using a long 3mm end mill in the Bridgeport to make a deep and wide slot in the end of the plug, so a really large 1/2" drive screwdriver socket could be used. About 150lbs ft seems to be par for the course.
HTH
Jon