That's honestly the BT I would've done, maybe PD at 7:45, but him waking after 1.5 hrs does sound OT, especially if he's crying for bed at 12:45. But, don't stress too much... if it's any consolidation, my bub does the same thing. I'm grateful bc he tells me when he needs the sleep even if I can not figure out WHY he does. In this case, we know that he's having NWs which will disrupt sleep to an extent. (FYI, we almost always have disrupted nights due to medical issues).
So in just a couple days we know that he's tired for his nap, why don't you keep nap at 12:30/12:45, and just push BT by 15 mins later than your old usual routine. And you totally know the drill, but let's do that and wait 3 days to see what collective data we can gather. What do you think?