Help: At the End of My Rope

I am so grateful that I found this website. Most of what I've read is very comforting, because hearing people's stories reassures me that I am not alone. I would love some feedback on my situation...

I have been married for 15 years to a man with ADD. I am at the end of my rope, and am tired of feeling like his mother instead of his wife. Everything he does drives me crazy, and makes me feel so unsettled, very unsupported, totally unimportant, and scared about the future. This is the opposite of what I want and need in a partner. That being said, he is a good man, loves his kids, and uses his extreme energy to work very hard (although he still manages to spend more than we make very month, always has and likely always will). We have built a life together that I don't want to walk away from, but I do not think that I can live with him and be happy at the same time. 

For years I have begged and pleaded for him to be more thoughtful and considerate, to act more like an adult and less like an overgrown child. To think before he acts. To consider how his behavior impacts others. But he always threw it back at me, claiming that he was fine and I was the cause of all of our problems (for example, I am "controlling" when I get upset about the $1200 tool he doesn't need that he bought at Home Depot when we are struggling to pay the mortgage. I have "issues" because I express fear for our safety when he forgets to lock our doors when he comes home late at night). We recently stumbled on his ADHD diagnosis when I, totally fed up with his forgetfulness, complete inattention to my needs and the needs of my children, and impulsive and reckless decisions that were quite literally ruining our lives, told him that I wanted a divorce, but was willing to try a separation with couples therapy if he would take a good, hard look at our marriage. He was willing, and we both started individual and couples therapy.

He was very quickly diagnosed with ADD. It was a HUGE relief, and I hoped that things would turn around and we could learn to live together and be happy. He is on medication, but often forgets to take it. He often misses his therapy appointments, but makes most of our couples therapy appointments, perhaps since I remind him the day before and day of. When we are in therapy, he always looks me in the eye and tells me how much he understands me and what I'm going through. Then, the minute we leave the therapist's office, he is off in his own little world again, making impulse buys that drain our bank account, leaving the doors unlocked and every light in the house on, leaving his dirty dishes in the sink and a trail of dirty clothes and garbage all over the house, and acting as if me and the kids don't exist. I feel like I have spent the past 15 years taking care of him, cleaning up his messes, and begging him to change. He says that he's trying, but no matter what he does and how much I beg, plead, or nag, HE DOES NOT CHANGE A THING. I have finally accepted that he will never change, even with the meds and therapy, and even though I cannot live like this. He is who he is, and I am who I am, and me + him = misery.

I have become an angry and resentful person. I am angry with him, and angry at myself for accepting my live in this emotional hell for so long. I feel like a single parent to our two children (one of whom has ADHD and is a real challenge, one that I must handle alone), and I have felt like a single mom from the moment my first child was born, though I didn't fully realize it until my second child was born). My husband has never been involved in our children's lives in a meaningful and thoughtful way, only in a superficial, fun-guy sort of way, when he's around. He is the fun parent, always up for an adventure, no rules or precautions, just one big party. My kids love him, and he loves them. I have learned to let go of the idea that he will be the kind of father that  I want for my kids. I have had to make up for a lot of neglect on his part. A big part of the problem is me: I am a very organized, cautious person and like to have things a certain way (neat, clean, orderly, and functional). I have high expectations of myself and those around me (within reason - I understand that everyone has limitations). I don't make decisions without mapping out the pros and cons, and weighing the possible consequences. He is the exact opposite in every way. When we met, I found his recklessness refreshing. Now that our lives are entwined and we have two kids, a house, and a life together, I feel trapped in a sinking ship. I want desparately to get out, but feel such guilt and sadness at the thought of divorcing him and raising my kids alone. It sometimes seems worse than living miserably with him.

I am not asking if I should stay or go, because I know that is a decision that only I can make, but I would love to hear thoughts from those of you who are or have been in a similar situation. I know I'm not alone, but certainly feel that way most of the time.