Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Sounds like you are going about it the right way!

Yes, heat can be your friend at loosing stuck screws, just don't think that a whole lot of heat would be better as it generally isn't. All you are trying to do is make the metal expand and more importantly, then contract again hopefully breaking any hold corrosion has on the threads. Several repeated moderate heating and cooling cycles and a few days of penetrant soaking should bring you the desired results, thus patience will definitely prove to be an important virtue in this situation!

Best of luck with what looks to be a worthwhile project!!!