Good practice to regularly take your gear apart!

This works. You might have to use a sledge hammer. I've had to do it a few times. You need to be a little creative to pad the foil with timber and stuff before you start whacking it.

I thought of making a special frame for using in case it became a common problem.

I ended up doing the job to fix loose foils. Since doing that all my foils fit beautifully and go together and come apart with a few taps of the mallet.

Have you tried to apply cold to your fuselage?
I'm not familiar with Gofoil, but especially if the fuse is aluminium chances are you can make it contract when thoroughly cooled down (ice spray does the trick) which sounds more promising than heating the frontwing in order to make it expand enough.

I had one beyond stuck because after I hit the bottom hard. It is likely you have a little hydraulic lock or slight misalignment and it will respond best to impact. In the end I used two outdoor benches so there was a little gap between them. Then holding the mast like an axe I could swing it down hard so the foil trailing edge hit the bench both side of the fuse at the same time and it came off easy. That was after all previous methods failed and it surprised me how easy it came off when the impact was on both sides of the trailing edge.

I found with a Slingshot foil that was prone to jamming; when a straight pull wouldn't shift it, I sat astride the wing and bumped the fuselage to and fro in a twisting motion while pulling it until it loosened.

I had one with salt/ice on fuse so what's that -10C (?), plus heat gun on wing to blister the paint, plus 100psi tapped into the joint AND mallet belting mast

No joy. So you have done well as some are actually inseparable

^^^ yes
two saw horses for the foil and hit the mast