It is horrible when you have to wake them, I have to do it too.
Ok then, plan. I would try and push out that first A again hun. The idea is if we're capping the nap slightly, we don't want too long of an A to BT. Also, we can't push too far of else he'll be even more grumpy about being woken!
So how about we do it slowly given his age. Maybe add 15mins onto the first A and still wake at 2pm and see how he fares for a few days? Xx