I replaced my main fuel line due to a bulge in it. Draining the tank is not a big deal. I did it outside the garage.

Sharp jabbing whacks are what are going to get this thing to let go. It may snap the hollow bolt, but that's going to be how you get this thing off...

Have you tried a stubby 8 oz ball pen hammer with a taught box end wrench? Good solid whacks. Imagine your target beyond the strike point. Go Mr. Miagi on this thing. Solid sharp blows. Quality better than quantity.