If he's done 2 12hr+ nights in a row I would stay with BT where it is 6.30pm. For now anyway. Let's just keep going on there an see where he gets over the next several days or longer.
This 11.5 hr night is confusing me cos it means jumping from an 11.5 hr day to a 12hr day.
Lots only do an 11.5hr night and if it's going to get longer it can take some time to get there. So if 11.5hr night is what he needs or what he can do your plan needs to put those 11.5hrs at a suitable time of night (hence the 7pm-6.30am or 6.30pm - 6.00am). And yes that can mean jumping to a longer day, that's just how it is, we have to have 24hrs in the day as that's the clock we run on. The longer day can actually bring on a longer night so it's not always a bad thing yk?
I know it is confusing, for all of us when we go through it, but even more so when you are as tired as you are. Please please take the full advantage of the time he sleeps and sleep yourself.
Please tell us a bit more about his NWs, usually around 4.30am?
How does he start the NW? shout/cry/snuffling around quietly then building to more noise/ screaming instantly???
Is there anything, anything you can think of which could be waking him? heating turning on or off, traffic noise, neighbours getting up for work, a local bread delivery truck rolling by outside?? Anything at all?
What exactly do you do during the NW and how does he respond?