Hi there
I have been keeping him up for about 3 hours before naps but if he gets up at 7am 3 hours later is 10 am. It seems late to start a nap at 10. What if he sleeps 2 hours? Then he's up at 12. Doesn't have throw the entire day off with another nap starting at 3pm?
As your LO isn't doing a 2hr morning nap I don't think this is an issue but lets say he did start to do two long 2hr naps per day, starting naps at 10am and 3pm is fine and he might be happy with a slightly shorter last A time (say 2.5hr with 7.30 BT) or if he needed a full 3hr A time then BT could move to 8pm. For lots of people this is a good routine as LO is well rested and although us parents might all like a 7pm BT the reality is that if a LO goes down happily and without a struggle at 8pm and sleeps well through the night, this is pretty attractive to parents despite the loss of 1hr Y time.
As LOs get older though and need that longer A time it is normal for one of the naps to become shorter, it isn't a sudden cut to one nap but more a period of transition where you keep one long nap (1.5hr or 2hr) and the other nap is shorter. This helps to fit all the naps and A times into the day.
From what I understand your LO doesn't sleep beyond 30 mins for any of his naps, is that right? So what happens then? You help him go back to sleep? or do W2S? or wait for him to call you then try to resettle? or finish the nap in arms/sling?
Also what is the difference between nap 1 and nap 2 where for nap 2 he is sleeping 2hrs (I assume you are resettling every 30 mins?) but nap 1 is only about 1hr long, can you not resettle that nap?
How are solids going? What times are you offering solids and is he taking much?
I would really resist putting him down for a nap until his A time is 3hrs or it is 10am. It sounds to me like he is UT for naps and not sleeping so well. At this age some LOs need more like 3.5 or 4hrs A time to be able to sleep well.