Hiya hun - so that was a better nap than the previous day & a quicker settle right? IIWM I'd give it at least a few days to let him adjust to the longer A before making a judgement as to whether its working or not. I think you might still need to stretch him towards 5.5hrs A though.
WRT the 5.5hrs A being too long, hard to say really. I think while he's only doing 5 in the AM & doing a 2hr nap its probably not, but as his nap has gotten shorter then it could well be. So you might want to pull BT a touch earlier (maybe 15mins) if he seems to be struggling. I think this is why you need to push the nap a bit later - so that as his daytime sleep needs reduce & the nap gets shorter, its not so long for him to last until BT IYSWIM?
As for the NW, for us, if DS is OT, we usually get NW's in the first few hours after BT, & then either restlessness from 4-5am onwards or we got EW. 3am WU's were usually teething related rather than OT. How long is he awake at the NW? Is he crying? I know from your other post you suspected molars coming, so could that be the cause of the 3am NW?