Hi there, sorry no one has responded yet! At this age, short naps are pretty typical. Many babies will take 30-45 minute naps and there's virtually nothing you can do to prolong them. It will end, that I can promise, if you just stick with your routine as it provides consistency.
If you are going to attempt any further tweaks to his routine, make sure you give a solid week/week and a half for each to see whether it is effective or not. Constantly changing baby's 'A' time will only confuse him and make him more OT or UT.