At that point I'd try just riding it, with the bolts out. You don't have to actually take it out on the road, just bounce on the pedals with the cranks horizontal, first right foot forward then left. Bouncing on the bottom pedal with cranks up and down might help too. Keep doing it and the cranks should quirm their way off, slowly at first. One any looseness is felt you must stop of course otherwise you could fall and hurt yourself.

After one crank loosens, you could re-install the fixing bolt on that side to keep going until the second one loosens.

I'm curious about how the threads got stripped. Was it from using a TA extractor, or the TA side of a multi-size tool like the old Park? A tool made to fit TA at 23.0 mm will seem to fit in a Stronglight, that wants a 23.35 mm extractor. Sometimes it'll even work to pull the crank, if it's not on too tight, leading some people to say the Park tool is a correct for for a SL crank. It isn't!

Like all manufactured things, the extractor threads on a SL have a tolerance, with some being a bit oversized and some under. Some folks here have sworn their SL cranks came with a 23.0 mm extractor thread, like that was one of the sizes SL made them in over the years. I don't know for sure, but I'm skeptical. We know SL switched to the Campy "standard" 22.0 mm extractor at some point (1980-ish?) but I have a hard time believing they made cranks with all three standards. Not on purpose anyway! But who knows, they're French...