Heat removes rusty fastners - cherry red, not a propane torch but oxy -acteylene. But I have always survived using a 4" right angle grinder or a dremel with the good fiberglass reinforced discs - cut the heads off and smash the bolt out. Sometimes you can tighten and loosen the bolt and nut with good sockets and they'll snap.
Any time you have tough bolts your first try has got to be your best. Quality sockets - use 6 point and penetrating oil. 12 point sockets or cheapos will always cause more grief. Good luck!
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country