If you don't increase his A time so he is tired enough to take a long nap, he will get overtired, just as you are noticing. The whole point of EASY is that baby's life is predictable. When you change things up, he can't self-regulate and take the sleep he needs when he's given the opportunity. He doesn't have the capacity to decide to sleep in if he's kept up an extra 3 hr in the evening here and there.
2hr45 is to short for him, we've already established that and you're just reinforcing that in my mind by seeing these short naps of 50-55 min after 2:45.
Please, please don't leave him in his cot to cry - I'm sure you're aware BW is totally against any form of controlled crying or cry it out - if baby cries for you, he needs you. Its actually really normal for a baby to need you, when he needs you, its important to respond to reinforce his trust in you - that's what keeps him feeling secure and safe which allows him to sleep and grow.
He must be nearly 7 months old by now, average A time would be around 3:15, so its definitely worth increasing to see how he goes. I know it feels wrong to increase his awake time when he's tired but its what has to be done when he's not awake long enough to take a long restorative nap.