Hi, it looks like you have a good teamwork approach going on, so I don't want to throw a wrench in it.
Just wanted to let you know I'm going through the EXACT same thing with my 14-month old. Her wakeups have been getting incrementally earlier, from 6:15/6:30-ish for the past couple months (which was somewhat tolerable) till the past 2 weeks which have been 5:00/5:15-ish.
She is very tired after about 3 hours of A time, so I've been putting her down for 1st nap around 8:15/8:30 am.
Typical schedule:
W: 5:00/5:15 am (I sit quietly with her in her room, lights off, and she is very calm but will not go back to sleep ... maybe I need to try do P.D. in her crib longer ... I give up after about 5 minutes because she is SOOO spry and awake)
A: 3 - 3.5 hours
S: 1st nap 8:30 - 9:15 or 9:30 (usually 40 minutes total)
A: 4 - 4.5 hours
S: 2nd nap anywhere from 1:00/2:00 - 2:30/3:30 (usually 75-90 mins total)
BT: 7:30
I have tried doing a 4:00 am Wake-to-Sleep which worked for us before when she was much younger. After 2 nights it doesn't seem to help, but I'll give it a few more tries.
From your thread, I think I'll try to stretch out her 1st A time to 4 hours, and 2nd A time to 3, and maybe an earlier BT (7:00?). It's difficult because I work and the babysitter doesn't always follow my instructions. But we'll give it a go.
fyi, she only has 5 teeth so I haven't quite figured out when she's teething and when she might just be OT. She has always been an angel/textbook baby, so we haven't gone through any hellish teething episodes. Also, I'm quite sure she's not hungry because I've kept her on a breakfast schedule around 6:30/6:45 am and she is quite happy until then.
If you have any more suggestions, let me know. Again, sorry if I'm interrupting a good flow you've got going!