Surely its easier for him working away, finishing work and having no childcare duties, than working near home, finishing work, straight into school run, clubs, cooking tea, homework, bath and bedtime?!
Have you sat him down and told him this?!
I was a single parent for 5 years with a 18 month old and 6 year old and I was working.....i didnt have any time off I was with the children 24/7 in the week when I wasnt working, and at weekends we went out on one day on days out, from busy theme park days, to the beach, playbarns etc to just a nice walk round a NT place, but we were always out and the other weekend day was spent keeping on top of the housework/washing etc.
Yes i was tired, every parent is, but you cant just opt out!
It seems very sad as youd think hed have missed the kids and you and it would give him a burst of energy!
Seriously sit him down and tell him it's not on! Sounds to me like he doesn't GAF and if you suggest splitting he'd be relieved! The only benefit here for you is you arent carrying round a load of resentment which makes you feel like crap.