I bought the $15 heat gun (I'm not a fan of using a torch on parts that are soaked with a highly flammable penetrant) from Harbor Freight and it makes a world of a difference. Heat cycling the bolt will loosen it. Get it super hot and try to take it off. If not, let it cool and try again.
Pretty sure the coils of the heat gun probably get above the autoignition temperature of the highly volatile penetrant. So just be careful.