Why won't my ADHD spouse get help even though he is making our family miserable?

My story is like so many others on here. ADHD spouse who is unreliable, lies, is a financial mess and never takes responsibility for his actions.

The most recent is that he drove our car for a year with an expired license and no insurance. WHY?! Because he missed an appointment to go to the next level with his license and he needed to start over so he instead just kept driving our children every day for a year. Till the police pulled him over for an expired sticker and he was discovered to also not have a proper license or insurance.

This is the tip of the iceberg of many fucked up lies that and behavior to c cover-up  his inability to manage his life. He has stolen cheques from me and forged my signature to pay rent when he had no money. He has not invoiced for months at a time when working freelance to the point of having no money. He took money from me to buy a car then said that car was stolen, but it never existed. He even once said he was getting treated for his ADHD but turned out he made up a therapist and was taking vitamins instead of meds.

He has not had a proper job in years and years. When the kids were in school I was forced to go back to work instead of him because he had no capacity to get a good job and didn't even try. By the way the kids are now going into gr 1 and he still at best has temporary and spotty employment. I have a very good government job and have been the main earner in our relationship since always.

I pay the majority of our expenses and only ask him for half the mortgage every month. He often at the very last second will say he doesn't have the money, or will only give me part of it. He never warns me so I am often scrambling to pay for things.

We own a house which I paid for, we own a care which I paid for. He never even has more than a hundred dollars in the bank. And he actually is completely unappreciative of these things. He constantly talks about how he does not want the responsibility and shows zero gratitude.

I am angry and bitter. And I scream constantly but nothing wakes him up! I recently had an emotional affair with an ex that lives far away and has his own family and my spouse suspected me and took my phone and read everything. That ex got freaked out that my spouse would tell his wife so he has now apruptly cut me off which hurts. I am mourning the loss of that relationship because at least it was a lovely distraction and something to look forward to. But even this is not enough to wake my partner up.

He won't even write in an agenda. Or do things to manage his ADHD. I bought him the ADHD and marriage book years ago and he won't read it. And when I get angry he says 'I am trying'. How is he trying?! I have zero attraction to him and I am depressed and just cut off. 

I've been trying to just focus on myself and what I need but it is so hard to not get dragged down by the constand financial stress my partner puts on me and our family. And his constant lies are devastating. How can I ever hope for happines when he is completely unwilling to take any action to make it better?