ADHD spouse seems to be floundering; can I do anything?

My husband's main source of income the past three years has been from providing companionship and some caregiving to his ailing elderly parents.  H has somewhat typical ADHD behaviors and symptoms:  difficulty keeping a good job; financial problems; denial of responsibility for his role in problems; difficulties with communication and intimacy; avoidance of certain kinds of responsibilities and tasks; comorbid mental health issues (depression and anxiety).  We have been living apart this fall but he was home this weekend because our daughters had just arrived for the holidays.  Both were out of the country all fall and will be home for no more than 2 weeks.  

This weekend, my husband told me the following:  (1) his father didn't want him to come home to see our daughters; (2) his father often expresses resentment about or resistance to paying my husband; (3) my husband has stopped taking his medications (and hasn't seen his therapist since this summer); (4) my husband doesn't want my help with exploring other long-term care options for his parents because "there are no other options" (his words); (5) my offer to help support my husband financially if he were to quit his current job (as caregiver) is insulting; and (6) my husband considers his situation to be hopeless.

I no longer think our marriage can be preserved or is even worth preserving.  But I'm concerned about my husband.  Can or should I do anything?  Is it him or his illness talking when he says he doesn't want any help from me?