Hi there, that sounds rough! Im not good at early starts so I sympathize.
From what I can remember, and please someone correct me,but it becomes a bit of a vicious cycle,the earlier they have that first nap the earlier they wake up!! Joy!! I get the feeling that he's making up for the early start with the nap, he knows he's got a nice long nap coming up so its all good!!
I would do one of two things, you could try just keeping him as busy as possible and deal with some grumpiness to make him sleep later, that's what I would do with my LO but she's a bit txt book and deals well with those things,or do over a longer period and push it later by 15mins every few days??
What do you think?? I think Tracy's first book has a good section about pushing naps.
When you've got the nap time later you can see how it is,if there is little change then you may need to shorten his nap??
I hope this helps a little bit!