Really interesting thread, so reassuring to know there are other people in the same situation as me!
My DH runs his own business and is very creative, works at random hours of the day etc. He works from home so as well as never switching off, he rarely sees other people. His excuse for not mucking in and taking more responsibility around the house / with DS: "I don't have space in my head for all that stuff as well" and to be honest I think he's probably telling the truth!
I decided I couldn't spend another year nagging him and feeling resentful, something had to change!
We're only three weeks in but I have found a weekly schedule has really helped and made a difference. He now has three nights a week when he can work / do research, one night a week to go to cinema with friends / meet a friend for dinner etc, and we have three nights together to catch up on tv/watch a film (I try to get a babysitter for one of the nights so we can pop out for a drink / meal). I have a night out on one of the nights when he's working, I'm going to try an exercise class for the first time in my life!
We each get one morning a weekend to ourselves - either lie in or go out and have some 'me time'. Afternoons at the weekend are family time and DH is banned from looking at his phone and computer!
I do just about all the meal planning and cooking because I enjoy it, apart from Saturday night when DH is in charge and will cook something just for the two of us once DS is in bed.
I no longer do his washing because I couldn't BEAR anymore "I've run out of pants/socks" comments!!!! He can use the washing machine and dryer anytime at the weekend, I use it for mine and DSs stuff plus towels etc during the week (one load a day, much easier!). I have also assigned him sole responsibility for dishwasher emptying, loading and turning on.
We also have a cleaner for a couple of hours a week.
All in all, life is a lot happier for all three of us now DH has clearer instructions on what housework is his responsibility, and when he is expected to spend time with us. I am also consciously 'stepping back' and letting DH lead our family time activities as I can be very bossy 
Sometimes it makes me sad that I have to prompt him so much to do what my friends' DHs do automatically, but this is who DH is, and I love him.