I would stick with the 5:45 bt even tho he was up earlier. If he decides to nap then you can adjust from there, it would depend on nap length. Is it possible that he isnt using enough energy during the day? I know when we have rainy days and M doesnt get to run around and really get a work out he wont sleep good, too much built up energy I think. It is possible that 11 hours is too long, but I doubt it. BUT if he is falling asleep almost instantly, then it could be. I just remembered a stage we went through, where if M fell asleep within 5 min, then he would have NW's. And whenever it took him longer than that to fall asleep, he would sttn. That wasnt helpful going back and forth was it, my thoughts dont always line up in order, lol.
I think in time he will tack on, it's just a matter of getting the right balance of exercise, sleep and restful periods. For example, M always tacks on BUT if he is getting a bit OT from all the nn days, he starts waking between 6-6:30 even tho he doesnt act ot at all. In that case, I will give him a longer rest period during the day and do bt 10 min earlier, last night he was in bed at 5:30 because he asked for it. He then tacked on and slept till 7, after 4 days of waking at 6-6:30.