I’d suggest - watching his wake windows and looking out for sleep queues, timing milk towards the end of wake windows so he can settle with a full tummy, stimulation when he’s awake (in a bouncer, or a walk, music, black and white story book/cards), doing bicycle kicks or tummy counterclockwise to ensure he doesn’t have gas, ensure that you’re feeling calm as babies pick up on that from mum, put him in a baby carrier and cover his head lightly with a muslin and go about your tasks (mine used to sleep while I Zumba’d!)
Is he becoming overtired? It might be worth looking at their awake windows, and looking out for his sleep ques x
Where are you trying naps? Only because when my first was 8 weeks, she started hating sleeping in the light (unless in the car or pushchair). Once I started putting her down in her cot in the dark, with blackout blinds (or sitting in the dark myself for a contact nap) then she was alright. It sounds like you’re doing everything right though, it’s just such a guessing game 😭