I agree, it's way past toast, don't even crank the engine again or you'll be looking for the broken teeth.

With that much play your piston-to-valve clearance isn't how you set it up - take a look for marks.

I've heard cryo treatment helps extend gear life, but no actual tests TIKO.

No matter how wet it looks with the cover off, believe me more oil can't hurt. Many older engines have directed oil (my 1958 Chevy 235 L6 stovebolt has a spray nozzle), or at least a drool hole above the cam to insure they're wet enough. Is there something like this for your engine?