Dear Zoe, thanks for your response - super-helpful, as always!
So I took your advice, kept slowly extending his morning A time to 5 hours, and he took a longish 1st nap (avg. 2 hours) and a short catnap (about 30 minutes) in the evening. This very often drove his BT very late (because initially I didn't cut short his first nap) so he would sleep at 10 PM and wake up at 6 am - but this was terribly poor night sleep so I started cutting short his 1st nap to bring BT under control, and that helped.
For almost a month LO (now 1 year old) yo-yo'd between 2 naps a day and 1 nap a day. However in the last 2 weeks, he seems to have settled into a-nap-a-day routine consistently. This has helped in the overall no. of hours of sleep he gets to go up, because earlier he had 3 A times of roughly 4 hours + 4 hours + 4.5 hours = 12.5 hours, hence a max of 11.5 hours of sleep. Now his A times are 5 hours + 5.5 hours = 10.5 hours, hence he can (theoretically) sleep for at least 13.5 hours.
Here's what a typical day looks like:
WU 7.30 AM
1st nap 12.30 PM
WU 3 PM
BT 8.30 PM
Theoretically, I said. Here's the problem: We have Extended Wakings every night now, from anywhere between 1 hour to 1.5 hours. They typically happen about 5 hours from BT. He wakes up, not crying, babbling to himself, starts whimpering after 10 minutes, one of us goes in to pat him, he quietens down (but isn't asleep), whimpers again the minute we stop patting. This goes on for an hour or so, after which he starts crying, and we take him in our arms and gently rock him, sometimes offer him a bottle if he's been crying for too long. Then we put him back in the cot, he cries again, we keep shush-patting till he goes to sleep.
Every night.
My guess is, he's not getting sufficient A time now, after being used to much more. Even during the month that he was oscillating between 2 naps and 1, on the day he took 1 nap, we would have an extended waking at night, not on the others.
However, if we give him more A time, doesn't his already low no. of hours of sleep get further reduced?
Suggestions please, these extended wakings are taking a lot out of us, besides affecting LO's night sleep.
Thanks again!