ADD post separation/divorce

I have reached my limit and although we are not married, we have been together for 7 years, have one child and one on the way ( I am 8 months pregnant).  I am leaving about one month after we have the baby, and we have discussed this.  The first time I tried to talk to him about it he was predictably angry.  He probably has no meaningful recollection of the reasons why I am leaving and unfortunately I can't really care too much anymore, I have a 3 year old and soon a newborn to care for.  The second time he said that he understood, but he's emotionally volitile (sic) especially within the past month so it's an on again off again situation.

Essentially we are having the same arguments we have been having for the past 7 years over and over again.  We are both tired of it, but I'm the decision maker of the relationship (more by necessity, than by nature) and so I have decided to end it.  It's not the arguing that has prompted this decision, but rather the fact that even though he is taking medication, vyvanse for the ADD and paxil for anxiety he is still having problems functioning at a basic level at home.  He lost the rent check, which was a cashier's check, my way of making sure bills were paid before all the money was spent.  He didn't make the car payment and in fact waited for collections at the loan company to call me before the payment was made.  He did a no call, no show at work which prompted his boss to call me 5 times at work.  I left work early terrified because the last time he did this he was suicidal.  Thankfully he was ok, just playing computer games all day.  I even called his mother thinking I might have to get her to come down if I had to call an ambulance.  I have no legal right to make medical decisions for him.  We had a fight that morning in which I told him that I needed to end our relationship, so I'm sure that prompted the temporary break.  He refuses to check his bank account on a regular basis repeating that he doesn't have the ID or password. So he overdrafts often or comes close. Nothing is stopping him from setting up a new one, and I have told him what it is multiple times, even writing it down and placing it next to the computer.

I have given up on making requests about personal hygiene, keeping the house clean, sex, having an appreciable emotional connection.  I just wanted to maintain, but now I see that I can't expose my children to circumstances so empty and unsatisfying.  Not to mention the emotional, financial, and physical chaos that we deal with day by day.  He refuses to admit that he needs to pursue therapeutic options beyond medication, that I am making a big deal out of these issues.  I know he is very stressed out by the fact that we are having another baby and this is probably causing the regression but he won't admit any of it, and this is really why I am leaving.  I have about 5 weeks before this baby comes, and especially after it's here I cannot have this level of chaos in my life.  I was sick for the first year of my son's life because I was so stressed out trying to care for all of us.  I just don't have room in my brain to care for a partially non-functional adult.  And an adult who can't or won't admit that they have a problem is basically dangerous and is doomed to repeat whatever mistakes they make as a result of the whatever issues they have.  

I am not seeking full custody, I am only going to go to court for child support because he has a history of money mismanagement and even though he would want to pay me on time he would forget or put if off and I need to have legal recourse to force him out of denial if necessary.  It's not the best option, not even a good one, but I will do what I have to in order to care for my children.

After all of this leads to  my question of how do we handle things once we are separated?  We work opposite schedules, so a basic joint custody is very workable.  When I work he will have the kids, when he works I will have the kids.  I will have him reimburse me for medical expenses and we'll both be responsible for feeding the kids etc. on our own.  

After 7 years it's going to be difficult for me to draw the line between what is my business based on how it affects the kids and what I really should stay out of.  I cannot be any sort of emotional support for him anymore, and folks with ADD need LOTS of emotional support.  Are there any resources that I can utilize to handle this in the best possible way?

One more thing.  This morning, I dropped my son off at daycare and his teacher said she wasn't expecting him to be there.  He likes to keep our son at home on the days that he is off which would be ok once in awhile, but according to his teacher he is kept at home almost every other day.  Well, they don't have a part-time option at our daycare, so we pay for the full week regardless.  He and I had a discussion about this at the beginning of this week which basically ended with us "agreeing", because apparently we didn't, that he needed to take our son to school everyday and pick him up in the afternoon, around 2 or 2:30 if he wanted to spend more time with him.  When I called him after dropping our son off, he admitted that he had planned to keep him home today.  Our son has allergies and they were bothering him yesterday which was his justification for keeping him home.  I asked when he was going to tell me about this, and I was answered with silence.  This has led me to rethink the whole custody thing.  If I can't trust him to honor his agreements about our son, or even tell the truth when it comes to his literal care, then I am not going to share custody with him.  I basically told him that if anything like this happened again we would be in court discussing custody.  Some days I feel that he is purposely trying to destroy whatever amicable relationship we might be able to salvage.