There are two possibilities, Sarah, and unfortunately no way to know which is happening.
He definitely gets a big drop from preshot to nadir and it could certainly be causing him to bounce at preshot. The only way to deal with this is to wait it out and see if his body gets used to the lower numbers and stops releasing its own sugars, lowering that preshot number. The only way I know to lessen the drop is to offer him small snacks around +4/5 and see if he flattens out.
The other possibility is that the insulin works to being him down but it is wearing out by preshot. The pmps you got on 5/10 suggests that. You gave a little more that cycle and he had a lower preshot number.
No way to know which it is for sure. But since it is the weekend and you can monitor, maybe try increasing and see if his preshot looks better without dropping his nadir too low. Maybe 0.8 or even one unit? Be prepared with regular food and gravy off higher carb foods just in case he dips low. If you'd get a yellow preshot and can monitor, try not to skip. If under 200, stall without feeding. Test in 20 minutes to make sure he is rising, not falling and if he is close to 200, then shoot a reduced dose, but shoot.
What do you think?