Hi KM! I'm following along to hear any ideas b/c DS is just the same. We've had lots of issues, but there are none left that I know of and he still wakes every 2-3 hours. I can't figure out why...
I'm interested to hear how your night goes after the one long nap... ?
The only thing that I can think of is that maybe you could try to extend your morning atime just a little bit. When DD was going through her 2-1, she suddenly started having lots and lots of NW and it was finally resolved by lengthening out her morning atime. She was always so tired for her first nap and would go right down and sleep a long time, so I never extended it, but when I finally did, her NW stopped. The only difference is that she was pretty good about STTN before that

The other thing is maybe he's actually OT and needs slightly shorter atimes... I say this b/c your 2nd two atimes are shorter than the first and yet you say he's grumpy in the evenings, kwim? So yes, I realize I'm contradicting myself here, but you could try one and if it doesn't work, try the other. I HTH and I hope you figure out what will fix these NW and when you do, let me know what does it so I can get Milo to STTN!!!