Hey Noah's Mom!
I think it is possible that he is getting too much sleep. Either that, or the timing of his naps aren't quite right. Most babies move to a 2hr A time at 4mo old, your lo is 8mo and is only doing 15min more than that, but his last A time was 4hrs. My dd is 11mo, and is still not doing a 4hr A time comfortably.
Most 8mo are doing around 3hrs of A time comfortably. Around that age, our routine looked something like this (I'll adjust for an 8am wake-up - ours was more like 6:30 because I work
)
A 8
E 8:30
A 8-11
S 11-12:30
E 12:30
A 12:30-3:30
E 3:15 - this was a split bottle for us, I found dd was waking early from the pm nap if she didn't get more bottle before hand
S 3:30-5 or 5:30
E 5:30 finish bottle from earlier
A 5:30-8 this was often a shorter A time for us. If it wasn't this one, it was the 1st one - and it varied depending on her age. This is still one of her shorter A times which is a bit strange, because most babies it is the first. DD is just backwards I guess
S 8 for the night
So it may be that he was overtired from such a long A time right before bed, but well rested enough from the naps to make him want to be up more. Some moms also find that they have to start limiting the am nap to 1hr if the A time between am and pm nap gets to be too long, or if baby only takes a short pm nap with such a long am nap. Our problem was that dd would fight the pm nap if she took too long of an am nap. I think I started shortening the am nap around 9 or 9.5mo, but all babies are different!
Hope that gives you some thoughts on what you might want to tweak. Let me know what you think and how things go!