I'm very sorry to hear about your situation. You sound like you really do have your kids best interest in mind. I hope you will be able to find some peace in it all. Regrettably, I'll be headed down that same path at the end of March. My wife and I are separating and getting a divorce. There's a lot of anger, hurt, fustration, etc. involved, but my overwhelming concern is for my 6-year old son.
My wife and I both love him dearly, of that I have no doubt. He is what has kept us together this long, but no doubt these next few months/years are going to be difficult. We haven't even told him yet and to be honest, I don't even know what the best way to go about it is. I want my wife and I to work out our schedule with our son and put him first. I want to have custody of him as close to 50% of the time as possible and more if I can. Starting out, my situation will be more settled and I'll be moving into a 2-bedroom apartment where he can have his own room. She's going into a situation that's more fluid and uncertain since she doesn't have a job right now and has to depend on others for some help.
I don't have a problem paying any amount of money to support my son, as I support him fully on my salary right now, but I've told her that I want her to share in the financial responsibility when she's able to and that all the money I give, I want it to be used on my son. not for her personal needs/wants. She seemed open and agreeable to this, but I guess we'll see how it goes. For now, I'll continue to pay his health care and tuition needs and we'll keep our joint checking account open and I'll put money into it for his other needs (i.e. doctor's visits, medicines, clothes etc.).
We likely won't go down the road of making the divorce official until after we separate, just due to financial reasons (neither of us have money for lawyers right now). But hopefully, when that time comes, we can dictate to the judge what we want in the best interest of our child and agree upon it instead of the other way around.
My hope is it doesn't turn hostile, but I'm not naive either. She has some friends that get in her ear from time to time.