I guess it probably doesn’t get that cold in Bundaberg but if you try it first thing in the morning when it’s coolest, freeze the extractor bolt in your deep freeze beforehand and use the heat gun on the flywheel that’d improve your chances of freeing it up.
They do get rusted on occasionally. I used to muck about with old cars a fair bit and found there was a crc penetrant product that worked a lot better than WD40. I can’t remember the specific label but I’d give rusty bolts and such a squirt every day for a few days and then found I had many fewer threads to rework and stud extractor kits were less frequently required.
The risky approach is to use an impact gun as that delivers shocks as it winds, risky because I’ve seen them pull the centre out.
