Where do we go from here? Move 10 month old to one nap?

My son is 10 months old and has been on 3/4/4 for the past couple of months. This was because his naps were crapping out and he was having long night wakings. It was working ok for us— he would still wake 1-2 times a night, but would go down quickly after nursing. He’s now taking longer to go back down, about an hour. And we’ve had to stretch his wake windows to more like 3.25/4/4.25. I’m pretty sure this is a maxxed out 2 nap schedule… but I don’t know if he’s ready for one nap or how to do it. I cap his two naps at 1 hour each, and most days I’m waking him up and he could be sleeping longer. If I let him sleep longer, however, his nights suffer worse.

Any advice on how to move forward? I currently have about 11-11.5 hours total awake time. I feel like putting him on 5/6 would go horribly at this age.

More info— daily wake time is 7am, bedtime is 8:15pm. He goes down independently/awake for nights and naps.