@Ohdostopwafflinggeremy i think the fact your dcs are comfortable enough to tell you what they think about their dad is huge. It’s a sign of the trust they have in you that they can confide about how they feel. That’s important.
I also think that somehow you’re still hoping your dh might get better, might finally get it. I have to say I agree with @Percypigspjs . Even if getting the ADHD diagnosis was to open the doors to change, this will take years for him to really change. We’re not talking about tweaking the edges there but really deep profound stuff, including working in all the protection mechanisms he has put in place over the years.
Now that your dcs have voiced their feelings that clearly, I fear that they’ll read staying as you not listening to them. What they’ll see is you staying iyswim.
And YY. tell them you disagree with the way he is reacting/acting. Stand up for them when he is hurtful towards them. Validate their feelings. That’s important!
But I would start looking at what life could be wo him. Both on a very practical pov (financial, house etc….) and by stepping back emotionally from him (not stepping up for him, trying to ‘save him’ by supporting him change etc…. That’s not, never has been, your responsibility).
Plus, things are stable just now re his health. That’s good. I’d be really mindful to not stay so long that you’ll end up caught up in the ‘I can’t possibly keave now that he is so unwell and getting worse’ scenario. Frim where I stand, it feels like you have an opportunity that you dint want to miss.