Hi Claire...mind if I pop in and offer my two cents?
The reason all of this is going on is because he is in the middle of a transition. This isn't how it's going to be forever; it's an ebb and flow: 2 steps forward, one step back until finally, finally he's able to handle the A time that a one-nap routine requires. His sleep needs are shifting, but his A times aren't ready yet. It is completely normal for what's happening to happen. It's normal for nighttime sleep to drop a little bit as they have more daytime sleep. I would be very hesistant to say that a 9.5h night--during this transition with two naps--is an OT night. He's waking earlier in the AM because he's getting too much daytime sleep spread out between TWO naps, not because he's necessarily getting too much daytime sleep, total-wise. Does that make sense?
I think what you need to do is keep his A times where he needs them. I know you're trying to figure it out still, but I wouldn't keep making his A times shorter. That will only prolong this.
I think your options are these:
1) Alternate one-nap and two-nap days. For example, he wakes up early on, say, Monday at 6am. That's a 2 nap day, which preseves a decent bedtime. He might still have a shorter night just because he got 2 naps that day, but an early bedtime does NOT work if LO is not a night sleep tacker-oner (how's that for a made up phrase?
). That's exactly how my DS was, so our days got a bit long there towards the end, but it was the only way we could get through the 2-1 until his A times were closer to 5h.
So, he does a 2 nap day. Then the next day, say he sleeps until his regular wake up time of 7. That's a one nap day. The next day might be another early day...so a 2 nap day. And so and so on.
2) Like Shiv suggested on Page 1, you can keep the set one nap and APOP a catnap every few days to keep the OT from building up too much.
Unfortunately, we can't force their little bodies to do certain A times...though, some can handle a bit of a push to a point; but eventually, too much is too much and we just have to wait for them to be ready to finish the transition. It sounds like your DS is able to handle longer A times (like the day he was put down at nursery at 11:15 and slept almost 3h), but just not every day. That's a good thing!! He's getting closer to being ready for 1 nap.
What really helped me--and granted, hindsight always helps--is to view the 2-1 truly as a progression and not so much a cut-and-dry deal. DS did do okay once he got to the 1 nap and 5h A times on each side; but the consolidation/convergence of the 2 naps leading up to that point was hard.
I hope that helps you a little bit, or at least gives you comfort that you're not alone in wanting to pull your hair out. *hugs*
ETA: Thought you might enjoy seeing my 2-1 thread wondering what in the world to do with DS (before then, I hadn't really posted because I just accepted the longer days/short nights). You are definitely no alone, hon!!
http://babywhispererforums.com/index.php?topic=172745.0