I think you're standing in your own way. You make clear statements about what she's doing that is a problem, and all of them are followed with excuses for her. You're part of this dynamic.
I spent years overseas and the first thing I noticed on returning to the UK was a shocking prevalence of "mental health" issues. I have never seen anything like it. There are more people who are "ill" than not in every aspect of my life (at work, at hobbies, etc).
I have used quotes because while, of course, there are people with genuine problems, the majority of those who trot out the mental health excuse are not dealing with anything unusual. Many seem to be looking for attention they don't get at home or (a related issue) are looking to explain why they somehow missed out on learning basic life skills. The point is, ADHD does NOT inevitably man that someone will behave without boundaries.
You've commented that you don't want to be one of those men who limits her money, but that is beyond ridiculous. You are in serious financial trouble because (not just once or twice but repeatedly, over years) she has overspent and has made no effort to change and you have made no effort to put the brakes on. I do not believe for a second that ADHD is responsible for this. It's a challenge, but it doesn't force families into destitution. You are both in an unhealthy dynamic.
Do not accept the all-too-common British excuse that she's "ill" and has no self-control. Marriage apparently began long before Jesus was even a twinkle in his father's eye as a business contract between families and you can see the financial chaos her behaviour has caused for you and any kids you have. You all need to play a part in changing this dynamic. For God's sake see a counselor and get one who specializes in financial issues. It's money you SHOULD spend--and I generally don't recommend counselling because it's expensive and hard-to-get.
She shouldn't be "looking" for a job, she should have one where she is working every waking hour to fix the mess she created. It DOES matter that you've been making money while she has been at home spending it. Being a SAHM mother is work but it is certainly not like having to hold down a job and do childcare and house-work. You should work out a clear financial agreement with the therapist where her access to money is very limited and only comes from what she earns (although she should be contributing mostly to paying off debt). As for you, STOP torpedoing your own and your kids' future stability and opportunities by putting up with this. You are partly to blame for this situation.