definitely sounds like he need more time awake
a 45min nap usually means he is not tired enough, a 30 min nap usually means he was overtired! If he was up for 2hrs and then slept for 45 min, but then up for 2.5hrs and slept for 30 min, I would guess his preferred A time is somewhere between 2-2.5 hrs.
Also it depends on how stimulating/ relaxed things are whilst he is awake. For example, Alex's normal A time at 6mo is about 2.75-3hrs. But two days a week his 3yo sister is at nursery, so it's a lot calmer and quieter at home, and then he can handle over 3hrs easily.
When he needs longer A time to counteract the short naps it usually takes me about 3 days of experimenting with different timings to get it right again
hth x