I would probably be quite specific with nursery. My DD is far more stimulated there and the carers have quite a lot to do and aren't always able to spot the small tired signs in amongst all the craziness. It sounded like you had a fantastic long one nap day with a three hour nap which shows he can do it - perhaps he need a that one nap earlier - nearer 11 or 11.30 particularly at nursery.
we found the 2-1 quite tricky as it was mixed up with nursery which does confuse things as they get so much more stimulation but possibly less outside time which can impact on sleep.
I think with today's nap it was quite late given the time of his WU, and he probably was quite OT by BT. EBT is worth a try - it never worked for us until dropping to one nap. I would have tried BT nearer to 6 after a day like today. Is that a possibility for you?