Could you install your computer in your bedroom, perhaps? Or, even better, in a spare room. Then just tell him you need unwinding time after work without any demands from other people, including him. State that you want some alone time, that it is about you, not about him. Assert your needs. Tell him you want to be left alone for a given period of time, then you will come and talk to him or whatever. Start with a short time, say fifteen minutes, and gradually extend it as he gets the idea
All that sounds awfully blunt. Maybe it is but sometimes one needs to be blunt if subtlety doesn't get the message across. I did a similar thing with my kids when they were quite young (still preschool)—I established a half-hour reading time in the afternoon when they were to play in their bedroom, which I'd made safe, and they were to leave me alone! Obviously I would have responded to real crises but there weren't any; they stopped coming to tell tales on each other and generally pester me with, well.... pesterings various! If they interrupted my reading time, I just reminded them it was my reading time and I would deal with everything later.
Good luck.