So you basically are getting a +10 test, but no PMPS test? There are a couple problems with this.
First, you don't have a PMPS test. We typically look at the before bed test (when you get it) and compare it to the preshot test, to see the rate of change. That rate of drop tells us whether the PM cycle will be an active one that either needs more monitoring or extra food to be left out.
When you are feeding him at +10, that is likely causing the insulin to wear off faster for that cycle, or lose duration. That would make the preshot higher than it normally would be. If you have to feed him at +10, try to make it no more than 2-3 tsps of a very low carb food. Neko had historically gotten a meal at what became our +9, so I eventually converted her over to some zero carb treats at that time.
I fed Neko 4 different foods (proteins) that I'd rotate through so she didn't get bored of any one of them. It also helps if for some reason the manufacturer changes the formula and kitty no longer likes that food, so you then have backups.