Oh man, you shouldn't have to hit it that hard. Are you sure you are getting some good leverage/pressure on the flywheel while you are hitting the crank? Maybe someone put Loctite on it. Heat will break it loose, but don't go crazy with a torch or something and ruin the bearings/seals.

Usually they just pop right off with a medium smack on the nut if you have good pressure against the flywheel when you hit it. Try the heat.

AV8TOR