Everything you are experiencing now, all the difficulties, are because he is on a low A. I am going to quote a fellow mod who is helping another mommy in the same situation, LO is also 6m old and A time is too low. I couldn't have said it better:
When you are upping A times the babies HATE it!! This is a situation where i say 'Mummy knows best!' I swear- my guy would STILL love to be up for 1.5 hours then sleeping for 40 mintues all day i reckon!! Once they are used to the A time push- this only takes a day or 2- they are much happier and sleeping better. Also- at this age they can seem tired and grumpy- when they actually need a change in scenery. My guy was a big fan of the 'oh- this is boring with boring old mummy- better go to sleep!'
So really you just need to stick to your guns. Yes, he does look tired, but think of it as if his sleepy cues are not reliable anymore till you have him on a better routine. I had to hold DS the last 30min of his A time on my arms because he was so fussy, but if I put him down when I thought he is for sure tired enough I always got an UT nap, I had to be so rigid with watching the clock.
WRT extending naps I would say 15min sounds a good time. I mean, if he is UT you are not going to manage to resettle him because he is not tired enough, and most of your naps are UT. I never managed to extend an UT nap
. Tracey said to try for 40min but I found that just messed with our routine and I didn't know when A time is starting and felt like I spent the entire day just trying to extend naps and not managing. It's depressing. But when I increased A time there was no need anymore in extending naps.
I would try and avoid the CN as much as you can, but if you have to have one then 30min sounds good to me.