I agree that the 500+ may have been a bounce from the green the night before. The numbers that evening were confusing - the green came early in the cycle. Did you do anything unusual after the green - like a little high carb food to bring it up? The numbers from the last two cycles are looking pretty normal - 300s to 200s - but generally a little high.
I'd say you have two choices, depending on whether you will be around to monitor. You can stick with the .8 and see what the next few cycles look like. It would be helpful to figure out why he goes lower at night. Is it because he eats less (does he graze or is he asleep at night?) or is it because he is more active at night (or less?) If you can figure out that, it may help bring down the numbers during the day if you can replicate it.
If you will be around to monitor, you could increase to one unit and see where it takes him. But with the unexpected greens, I would want to be there to intervene with food if necessary. (If he got down in the 40s, you would try some regular food and test again in 20 minutes. If he'd continue to drop, then try some gravy off higher carb food and come on for advice.)
What is the feeding schedule? Does he generally graze with the wet food - during the day and at night?
Although his numbers present a challenging picture, don't lose sight of the fact that he is getting good numbers and is not even on one unit of insulin. And as you say, he is feeling and acting good. You both are doing great - just keep remembering that "it's a marathon, not a sprint" thing.