7.30 is OK, and you can try earlier on the other days.
I would have said that as he is not yet 2 you can expect the nap to come back unless he is exceptionally low sleep needs?
You could try pushing the nap back by 15 or more mins? We also struggled with UT and if he went down UT then a nap was so much harder than OT! It could be that he is UT and then gets himself OT (hence the energy as the adrenalin kicks in!)