Hi there! I think I tell you what the problem is, your little guy is not awake long enough. He's not tired enough to go to sleep. Most babies his age are awake for at least 3 hrs and he's only awake for 2 and a bit. I can see you have him on a 12 hr day which is great so I would recommend you get him out of the house in the morning and extend that morning A time and you'll get better naps. It'll probably take about a week for everything to settle down, between you pushing his A times and the sleep evening out but you'll likely notice results quite quickly. Most babies drop their CN by 6 months so he's long overdue.
Swimming is a great activity for keeping baby awake because it's a such a sensory wonderland. Music class or a play group is great fun too. I found walks were a little dicey for my boys just because it's a little too soothing and they'd fall asleep but maybe your LO doesn't. I'd extend his A time by 30 minutes right away, across all A times and 4 days later push for another 30 minutes. At that point you will definitely need to drop the CN or your nights will go out the window!
