So either his body has finally figured out how the insulin and food work together, or his pancreas is waking up. Regardless, you have a unpredictable situation.
I wouldn't give him a shot tonight. He is still dropping so the insulin is still working or his pancreas is. He may be high in the am (after 24 hours since the last shot and/or because his pancreas got tired and went "back to sleep" for awhile.). Regardless, I would reduce the dose in the am - maybe .5?