I'm guessing that waking early in the night is definitely due to OT.
So, no he sleeps from 9:30/10 - 11:30/12 and then nothing til bedtime at 7:15? That's such a long stretch - I'm sure it's that OT that's causing the NWs. I suspect the 2:00 nap is now too early for him to have another nap, and perhaps even that an hour was too long. Usually when mums are doing the 2 to 1 nap switch, if the am nap is the longest, then the pm nap is super short (like only 30 min). Would you be able to do a quick catnap when you get back from your school run?
You mention that you do a school run at noon, how long does that take? I think ideally , you'd like to get him to the point where his nap is after that school run - so that's quite a shift from going down at 9:30/10. What you might want to try is shortening that am nap (leave it at 10, but start cutting it shorter - just 15 min every few days) and that may help him take an earlier pm nap - before the afternoon school run. So eventually, that 10:00 nap would only go til 10:30, then he'd take a longer nap between your noon and pm school runs. And then you could cut out the 10:00 catnap, and he'd have his long nap in the middle of the day.
I'm also concerned that with a big long sleep so early in his day, that may eventually cause EWs - some mums find that if the first nap of the day is too early and too long, it acts as an extension of night sleep, so some bubs wake even earlier in the day. And 7 hrs of A time is really, really long. My dd is 2.5 and she cannot do 7 hrs of A time without getting super OT. So if we can figure out a way to shift around your day around the school runs, I think we can balance out his day a bit better.
Would either of these routines work (or at least be worth a try - give the school runs)?
6-7 wake
10 - nap (shorten it gradually, to get down to 30 min)
12 - school run
1 - nap (this would be the long one, you could even start it at 12:30 if you're back, he can have dinner before you leave for the school run)
7ish - bedtime
if his 2nd nap goes til 2:30 (I don't know what time you need to leave) That cuts his A time to bedtime down to 4.5 hrs, which is much more reasonable.
or.....
6-7 wake
9:30/10 - long nap (don't wake him)
2:30/3 - school run (I don't know what time this is)
3:30 - catnap (wake after 30 min)
7ish - bedtime
again, that last A time will be much shorter....
It can be confusing to arrange things around all your other kids, so I'm just tossing out options to see if something might work. Hang in there! It is possible with multiple children