When we moved to 1 nap (which was early) the nap was short like yours but it was just about impossible to get 2 naps. I just ploughed through with the short nap and EBT.
We were the same here - took a good few weeks for the nap to lengthen so just had to ride it out in the mean time.
One thing I will say is that I have found with DS his early waking is very strongly linked with the timing of the nap. If he naps early, he wakes early. I do wonder if that is the case with your DS, KM. I know you have the issue of him short napping if you push the nap post 11am, whereas before then he'll nap for longer BUT doing an early nap is likely keeping you in the early waking cycle. He will always be shattered come BT because his PM A time was too long, and he'll wake early because he can catch up on his night sleep with the early nap. The combination keeps him in an OT loop.
For my DS, pushing the nap later (gradually 15mins/week) helped break the EW cycle. We had to do this at exactly this age, & went from an 11-11.30am nap to a 12.30pm nap over the course of 6 weeks. We had a few hellish weeks of OT while we pushed the nap to lunchtime, & then he suddenly started sleeping in til 7am. I never believed it would happen but it did. Is that something you would be willing to try?