I’m sorry but I really don’t understand this as a father of newer twins. I had them solo at day 4. Taking a shower or getting essential small things done (like a necessary load of laundry) wasn’t a problem. At that stage it’s change, feed, nap then 30-45 min of them sleeping or being calm then repeat.

He has to be taking multiple naps throughout the day. As soon as he goes down do what you need to do. Showers take 10-15 min tops. Dishes and most other household activities the same. If he cries for 2 min while you hop out of the shower or drop what you’re doing he’ll be just fine.

Use the opportunities he gives you when he naps (no matter how short), prioritize your health (i.e. showering, naps for yourself) and necessities (food, clean clothes). Everything else can wait including family visits, cleaning, etc.