If it were me, I'd swap positions of the injectors for working and non-working cylinders and see if the problem moves with the injectors.

Failing that, I think we're back to trigger point issues, perhaps sticking pivots, or a worn distributor shaft bushing. I don't understand the worn "prong", I don't think anything is spinning or sliding there. Perhaps the prong sets the position of the points tray properly relative to the cam, and poor alignment is causing triggering problems...