Now what?

Im still new here but have a few ?s:

My husband was diagnosed with severe adult ADHD recently, to noone's surprise but his own. He seems to have taken it hard.  He has memory problems already due to encephalitis in the past, but I don't know how much more I can take.  Even our 7 year old cant stand the chaos that follows his dad everywhere.  My marriage is over I'm afraid.  The only reason I stuck around this long was to get some finances in order.

His therapist recommended at least trying the meds, but hubby wants to "think about it," and that was two weeks ago.  Finally today I just made appt with his doctor, even though he said he could (then why didn't he two weeks ago?).  when I told him, he sounded relieved, which leads me to my questions:

1.  Is it the ADHD that he refuses to ask for help?

2.  I can't finish 1 sentence before he butts in and says, "I know.". My nephew with ADHD also "knows" everything, what the heck is that about?

3.  I'm not going to get my hopes up that he even makes it to his doctor appt, however I was wondering even if that happens and he starts the meds what, if any expectations should I have?  

4.  I also get so very stressed out having a conversation with him.  He jumps from topic to topic, starts stories at the end and takes forever to tell them, by then I have completely lost interest on top of a pounding headache from the topic jumping.  Is this the ADHD or just lack of social skills?