I'd keep trying for the CN hun. Even the quiet time in bed I think helps and do EBT.
I'd also keep trying to extend that first A too. 15mims again, then after another couple of days, extend again. It is yucky this stage in the transition and some OT is to be expected but you are giving him the opportunity to sleep, it's up to him to take it. There's only so much you can do hun, I feel for you though I got really fed up around that stage of nap refusal xx