Hi there, I think it may be a combination of prop and a UT/OT loop. At 7mo, I would expect him to have an A time of around 3hr, maybe a touch more. He's sort of doing that in the morning, but maybe not always and even with your help the nap is not always a full one (naps of 1h15min are often UT at this age). His second A time is also short at not quite 3hr. So, as you're working on independent sleep, I'd start pushing those A times out to 3hr and just get rid of the CN (he can still have a rest if you think he needs it, but hopefully with the longer As and more restorative naps he'll manage better in the early evening).
How do you settle him at night? How many times are you feeding?