No such thing as Adult Diagnosis?

after years of therapy, and 22 years of bullying and the roller coaster that I've come to learn is ADD without the Hyperactivity component, I convinced my husband that this evaluation and diagnosis could save our marriage.  Additionally, our children are learning to behave like him, and they're just horrible!!  Unfortunately time passed before the appointment, his interested lessened, and he manipulated the situation so that I couldn't go with him.  He came home and said the therapist told him you can't diagnose an adult with ADD if they were not diagnosed as a child.  He said my husband likely has "anxiety issues" and made him an appointment with the psychiatrist for February, 2 months from now!!  He wants to do marriage counseling with us, which we've done with numerous counselors.  I can't do it.  I can't last 2 months, I can't last 2 weeks.  I agreed to give our marriage on last try, because he promised we would go to this appointment together.  I needed this as much or more than he did, it was for us, not him.  I had an apartment lined up and I let it go, I have no trust in him at all.  If this counselor actually told him this, then he must be a quack right?  And if he didn't, then I can't trust my husband and I need to just let him go!  I'm having a horrible time finding a counselor in our area that is familiar with adult ADD, I'm really really frustrated, and absent a diagnosis I'm done.  He asked me what happens if it turns he "doesn't have this" and I told him we're finished.  Absent some explanation, I have to walk away and try to save my sanity before I leap off a bridge.  Who does the diagnosis, and is it true that you can't diagnose an adult who wasn't diagnosed as a child?  Also, is it true that anxiety is treated the same as adult ADD both cognitively and with medication?  Finally, if this guy is a quack, how do I find someone who is not?