Agree with everything: don't stay for the kids, but do run through all the other options first!
I just wanted to share my experiences really - dp also works from home and I can really see where you're coming from. Currently I also work part time from home, but I don't think I could handle being a SAHM while he was working like that. It's not just the proximity (like I say, it seems to be fine when we are both working), it's a control/ hierarchy thing I guess. It used to drive me mad that he was allowed to chuck strops and throw things around the office with dd in the next room, when I had to keep it together at all times. Plus his work always took precedence (OK, so it pays the rent, but it did wind me up).
I hope at least some of that makes some sense anyway - suffice to say that I think the vast majority of marriages would hit problems in your situation. Obviously you can't diagnose such things like this, but I also definately think that depression is a possibility.
So, apart from Relate, my suggestions would be:
-Can you get some regular time out of the house? You need more than a couple of days to yourself - I think you need a regular (once/twice a week) time when you get to do something different, with or without the kids. M&T group? even a part-time job that only just pays for the childcare might do you good.
-Actually that's it - other suggestions would come through the Relate counselling. Also might be worth asking your health visitor about the possibility of pnd.
PS this might sound twee, but I could be a good thing that you "really hate him". It's when there's no emotion left that you really need to worry.