Since he dropped to 76 after stalling, and we know he'll go sky high if you skip, I'd go ahead and feed him and give him 0.5
I think you can usually test until about +2, so get a +1 and +2 so we know what food to leave down for him.
In the morning, I'd go back to the 1U dose and hold it for at least 6-10 cycles (depending on how he responds) unless he drops below 50 at any time.
We've got to find a starting point for him that allows him to get his shots twice a day without having him drop so low at night that you can't shoot since I know you really can't stay up due to your cancer treatments.