Best thing to do at this point is pick a time and stick with it. If you don't want him up any earlier than 6 am, don't go to him until then unless he's crying out to you, then resettle if you can. We've had to do that with our lo for awhile; she'll usually resettle and fall back to sleep on her own, then sleep longer than we expect.
Also, what time is bed time? He should be getting around 11-12 hours of sleep at night if he's not already. Not getting enough sleep during the day and night is usually the culprit behind early wakings.
For naps, I would see if you can drop that cat nap completely all the time. It really depends on how long he's able to stay up; I'm thinking if he can stay up 3 hours or more than it's time to drop it. At 7.5 months he *should* be able to stay up for more than 3 hours, but every lo is different. Most lo's drop the cat nap completely between 6 and 7 months.
As for regular nap times, what I would do is start going by the clock more. 9 and 1 are good biological sleep times to start with, but the nap can start anywhere around those times within a half hour-an hour or so. I noticed that a lot of lo's with 2 naps start their second nap around 2ish. Pick a schedule, and try and stick to it within about a half hour or so for most days, regardless of if he takes a short nap on you.
Hope this helps a little!
*HUGS*
Sonya =P
