if you have the right tool for it, put the tool in the vice to hold it firm and use the wheel to get the torque to un-screw it,
if you dont want to keep the freewheel intact, squash the fook out of it in the vice and twist it of using "b.f.a.i"
you could try soaking the freewheel in anti-seize, watch your bearings though, it'll even get past the snuggist of seals,
good luck