If he's still having 2 day naps, it sounds like he's definitely ready for only 1 nap now....with that nap, when I transitioned DD to 1 nap (around 13mths as she was fighting that afternoon nap so bad!!) I would push her sleep out until 11am and then eventually later and later until lunch time.....took a bit of time. But by the time DD goes to bed these days, she's so buggered she usually doesn't fight it (around 1230pm she goes down). If she does fight it, then I don't bother lying with her for too long, I get up and try again 30mins later. BTW, my DD won't feed to sleep anymore, not since she outgrew it at 11mths (much to my dismay at the time!!!).
Only way to get her down is to lie with her, we read 2 books and then I say time for a sleep and we lie together.....

Why don't you introduce 2 books to read to him every day before his nap time? Like having a night routine....but it's a day routine? It helped us

Remember too, when you're feeling stressed about him not going to sleep (and trust me, I've had many days like that so I know how you feel!!!!) it only makes it worse as he picks up on your stress levels and it makes him only worse.