If he has never really slept past 45 mins, that may be the issue here. We also started set naps around this age; with the morning nap starting around 9am; despite the wake up. So, even if mine was up at 5.30am, I would do my best to stretch her to 9am (15min variation). By doing that, I was able to keep our day consistent more or less rather than constantly adjusting things. If your LO wakes early from the nap; try leaving him in the cot for another 15-20mins and see if he will put himself back to sleep. You won't be able to drop the catnap with 2 short naps, it may be possible with one longer nap. With regards to stretching A's, I worked on 1 A at a time, starting with the morning A - so I would try adding extra 10mins every couple of days, try taking him out of the house (if possible) and doing a longer windown routine when stretching A's.
HTH