I'm not sure I can speak to how to separate, so sorry not answering your direct question. But I am 40, almost 41, and been married twice. My first husband and I were married 8 years and divorced having no kids. Loved each other tremendously, I could now say. my second marriage almost crumbled many, many times. We have 3 kids, having just begun an adoption of our 3rd a 5 month old. We also have a 4 and 6 yr old boys. We've been married 11 years and together 12-can't believe we made it this far.
My strong belief is that "to stay married, you stay married". There is no secret to marriage beyond that. I firmly believe that when you have kids it is the hardest time in a mom's life and in a married life. No matter what it's a lonely experience. It's completely amazing wonderful, of course, but it's just in itself hard on a marriage. Hard on each spouse. It takes away from what you used to give to each other and to yourself and resentment happens no matter what. perhaps it opens up your own personal pandoras box, and his. Sometimes its unknown. I can tell you, IT GETS BETTER!
If you two can separate and stay in teh same house, all the better. If you move out, you'll likely never recover your marriage. But truly, in time, things tend to improve. As the child gets older, you'll get more freedom and you'll both be glad you made it thru. I guess having been divorced before, it's excruciating. It's an experience I wouldn't wish on my enemy.
We almost divorced 3 times at least. We too were dependent on each other and never left the house or moved out. You're biggest challenge is the fact that your spouse wont talk to you. I would suggest just giving him room if you can be strong enough for you both. I have come to believe that one of us is usually taking the 'strong lead' and carrying the other.
No disrespect intended, but I think you/he could find a reason to walk away at any time. It's usually about respecting him or he respecting you.
It's good to be married and have your kids in school. You'll get the time back to share of yourself and for yourself. Date nights really help too if you guys can get to that point. Would be good if you had a friend who could take your chld for a night to give you the quiet time to see if your spouse would open up with out the baby around. Even 2 nights.
If you get to a place where he wants to work on this too, I strongly suggest vacations even as a family. There is truly something to getting away from your responsibilities, each of yours, to see that you do really like eachother, not just love each other. And pull from that any time you get discouraged. We go every year even if its just to a hotel down the street with a swimming pool for the kids. Or camping. It gets us away from our life. :o)
Anyway, hope that helps a little.