Diagnosis and treatment ... then what?

Hi all, I'm new here.  My husband is in the process of getting diagnosed with ADHD.  A little background: we've been married 6 years, just had our 2nd child 3 weeks ago.  He moved out when I was 3 months pregnant and just moved back in about a month ago (yes, our relationship has gotten that bad) - this was the third time while pregnant that he said that's it, he was leaving.  I said fine, leave - my prioirity needs to be safety and stability for me and the kids.  I am exhausted from overfunctioning to compensate for his ADHD symptoms.  I am emotionally done.  Burnt out.  He moved back in, but it was not a red carpet, hallmark-move moment.  And I'm not convinced our marriage will last.  We cohabitate and raise the kids.  I'm glad for the forthcoming diagnosis and treatment, but I fear a lot of things:

1) what if it's too little, too late?  Can I repair the marriage?  What if I don't want to?  Does that make me a bad person?

2) once the ADHD gets addressed, what about the other dysfunctional relationship patterns?  I fear that the ADHD will be the easy part to address - I fear the rest of the non-ADHD-related dysfunction will be the hard part to change.

3) my parents were divorced when I was a pre-teen.  I had (have?) so much anger towards them, I felt orphaned, like they failed me as parents for divorcing.  **I don't want to do that to my kids.** How do I get past this to make the best decision for my family?  Am I doing them any favors by continuing to invest in a dysfunctional relationship?

Thanks for listening, and for any wisdom you have to share.