ADHD and Addiction

I'm new here and am in the process of reading the book Melissa Orlov wrote. I'm the non-ADHD one in my relationship. My partner (we suspect) had it and also seriously struggles with addiction. As I'm reading this text as well as other texts on ADHD, I'm finding out that addiction is extremely common among people with ADHD and yet it is not discussed much. I'm at my wits end with my partner. The ADHD on its own is challenging enough but then the addiction....,which has been getting steadily worse. Can a relationship be saved when both are factors in destroying it? What do you even do? Im unfortunately in a position where I can't leave him (I should note that my safety is not an issue). I don't trust him at all. I have next to no emotions left to spare that's how done I feel. I care, but at the same time I don't want to live this miserable anymore. Do therapists treat both adhd and addiction simultaneously? He's been to rehab multiple times. He struggles with undiagnosed/treated depression as well. He knows what he needs to do, but won't do it. Is that a sign I should find a way to get out? Can this even be fixed? We have a child together. I want our child to have a happy home and right now it's not. I don't know what's best for us. Can anyone advise? I'm so broken.