Hmm , I see the keyway has been wallowed out on the left side . That should be repaired .
I had the same on my crankshaft . I welded the left side of the keyway and had to hand file it back to proper size . No more wobble of the key .
I also see the taper that the flywheel rests on is pretty pitted . How does the corresponding area of the flywheel look ?
In order for a better hold of the flywheel , you should consider lapping the flywheel to the crank tapper . That should smooth both surfaces , resulting in a much better fit . It's that fit that actually holds the flywheel from turning . The key is there to simplify timing .
As for your spring pushing the cam outward , try the tape I suggested .
Pete .