Looks like a good decision - always better to be on the cautious side when you don't know how he will react. He did pretty well on the 26th with a similar PS and 3.5u (which I think was too much), so, hopefully, he will be fine today.
I think you are seeing the clearing of the "mess" made from the combined insulin dosing that was probably having him in a chronic state of rebound defense. And if you took up the dry food, or reduced the amount, that is also a factor. I suspect that things will continue to be in flux for a while while you are finding his new, best dose on lev alone - so be patient! It should all settle out eventually. Unless he is headed OTJ again, then all bets are off!