ProZinc itself is the problem - I'll explain in a bit.
The numbers are still too high, I would not let him go without insulin any longer. Very serious risk of DKA. The 76 was a clue he went much much lower the night before, so some sort of reduction should have been taken. All those lower than usual preshots are clues he went lower and probably/definitely needed reductions.
I believe the ProZinc is just too harsh for him and he will just keep bouncing and bouncing. We say give it 3 months of a good effort, it's been more than that and I'm not really seeing any progress.
Time to ask about Lantus or its generics. You would need new syringes, we can help with that when you're ready. It may take some time to see progress on Lantus, because it's strength is flat cycles, not necessarily bringing high numbers down. So know that going in, it usually takes 1-3 months on Lantus to see at least some progress.
In the meantime, do try to get at least a before bed test in. His low numbers are most often at night.