Thats a tough question, I remember back then we were all the over place with sleep. I think Ash was having roughly 3 naps day but only for 40mins at each.
I think its hard for them at that age to resettle themselves thats why he may wake frequently. When you first put him down how does he go to sleep? I used to feed Ash to sleep at that age so therefore whenever she woke she needed the breast to resettle.
Just try to go with the flow, I know it can be stressful, I used to always worry Ash wasn't having enough sleep and it didn't help when I had MIL telling me my daughter had bags under her eyes cause i wasn't letting her sleep enough.
Does he seem really unsettled in between as though he needs more? When he wakes from his naps what mood is he in? Although Ash had only 40min sleeps she would wake happy and there was no way I could settle her for longer.