Oh yeah, you had to give the HC, don't criticize yourself on that one! You learn, like you are now, how much to give to get enough of a rise without going high. I once sent Bix into the 300s with HC, but that's how you learn. Better to go that way than not to treat a possible hypo.
I don't know that I would stay with the 11%, though I think it's fine for tomorrow. Do you think these lower numbers are connected to a change to lower carb food? I'm not sure what the sequence is, but if he was on slightly higher carb before and you've dropped it, that could account for not needing as much insulin. I would want to go with lower carb and lower dose, but for tomorrow do what you need to to keep him safe and not be worried all day!!!