Oh boy, that's a toughie. I really don't like that you're gone for 12 hours Saturday 'cause if you give a half dose Friday at 10:30 (not sure how long it takes you to get home and prep for shot) then turn around and give a full dose shot 7 hours later, you're causing a bit too much depot (shed). And you can't go home mid shift to check on him, can you? That was pretty much always my trouble too.
I guess you could do another half dose for the Saturday AM shot, but then that one has to carry him over for 12+ hours. Maybe each shot could be 3/4ths his dose? 1.5U then?
Kind of thinking "aloud" here. What do you think of the 1.5U dose both Friday night then Saturday AM? That much seems like too much to give 7 hours apart, but you know how he's doing on 2U and he appears to be staying fairly high on that much, so it's probably OK to do 1.5U that close together. That's a 25% decrease. The idea is to not give so much that he would go low, but give enough that he doesn't get so high over the 12+ hours Saturday.
You will do splits Friday at 9AM & 10:30AM, if that's 12 hours before you'd be back home and can give the PM shot.
Does that seem safe and doable?