45min/1h A times really are too "young" of an A time for age. I'd really try to start afresh in the morning with that first A time, keep him up for 1h15 (that includes eating, activity time, and wind down)--so he'll need to be asleep at the 1h15 mark. If he short naps (anything less than 1.5h), I'd only try to resettle with shh/pat for about 20 minutes. If he doesn't go back to sleep, get him up, feed him and have him asleep at 1h15 A time. Do this for 3 days. Then on the 4th day, up his A time to 1.5h and see how that goes.
I think they can show tired cues out of habit. He might be toucy and therefore needs to extend his A times more slowly, but I definitely think he can handle more.
What is his room like when he's sleeping? Is it darkened? White noise? Is he swaddled?