Poor you, this sounds awful. I also have a 2.5 yr old who went through the whole messing around at bedtime, not wanting to go to sleep, and only finally going to sleep about 9.30 - 10pm. We had to cut her nap - completely - the first days were hard hard work as she was shattered at 6, and getting her to 7pm was difficult. But she went straight to bed and straight to sleep. She is at nursery two days a week and has an hours nap and we do find that she can be a bit more difficult about going to sleep, but generally we will put her to bed 30 mins later and put up with a bit of shouting for mummy/daddy.
I would really ask the nursery to cut his nap to 45mins and see what happens if he is tired. I would also not go in if he is just playing - I know it is difficult to just listen to them messing, when you want to have an evening, but on a the days where she still plays up, I simply walk out turn off the light, and say I will come back when you want tucking into bed. Doesn't usually take more than 5 mins. It is also helpful that she can't open her bedroom door - this may be something.
The NW after this sounds terrible, and I don't know what to suggest - what does he do at each waking - cry? want something?