Oh Straffles, since today was with a 45min nap, then run with it for a week. Consistency over anything else now, this would be my advice.
Now from DS history, even horrendously OT, he does not go less than 8hr30min at the moment.So, perhaps you are right, it can't get worse than 8hr45min with your DS. Now, this is just to let you know how I deallt with his last 8hr30min night 3 weeks ago,
WU: 7:30
Nap: 15:00 - 17:00
BT: 00:30 (we were at a wedding banquet)
WU: 9:00
Nap: 15:00 - 18:00 (much shorter morning A time, had to wake him from nap!)
BT: 21:20
WU: 8:20
He recovered with the 3hr nap and 11hr night. We are doing option 2 at the moment. That is, late but full nap and shorter night. I don't know if this gets us the most total sleep but we are in a predictable OT/UT loop. Kinda like predictable chaos
he does 3-4 shorts nights (9.5 - 10.5hr) and then a longer night (10.5 - 11hr). His naps are between 1.5 - 2hr. I will keep doing this until I can make a better guess at his nap length and start capping. I tried capping to 1hr15 a couple of weeks ago and it still gave short nights. So I figured he might as well have a full nap
at least the sleep total is higher!
We have always stuck to a 9:00 put down in cot though. So we have kind set BT. This is what our routine look like with option 2.
WU: anything from 7:00 - 8:30
Nap: anytime from 14:30 - 15:00. Wakes between 16:30 - 17:00
BT: put down at 21:00, asleep from 21:15 - 21:45
Again, my advise would be to stick to what you are doing. Cos consistency is really more important now. If one needs to troubleshoot a problem, one needs to have a place to start. So let's start with 45min nap. I put our routine down just for you to have a look.