Setting boundries ....The hitchhiker's guide

Just read this response in another post, Melissa's  response was in context  to respond to someone with a lot more on their plate due  than ADD spouse to life circumstances.  However reading this left me with questions on the "how to"  after another night  of being recipient of anger/blame behavior from DH with ADD for some minor problem.   The quote is....

"As for your husband's desire to address his issues, you have the opportunity to move forward as you wish, and be supportive of (but detached from the outcome of) his efforts.  He should address his ADHD whether or not you stay together, and it's very freeing to say "I am going to live my life as I see fit.  You may come along if you wish...but I'm no longer going to adapt to your poor behavior."

 I am looking for some practical advice on how set boundaries around acceptable behavior in the household if you are choosing to stay. What do you do when DH goes off about something that is a)  a problem he could have seen and addressed yet gets angry about/needs to blame other for and b) not a big deal anyway.... My coping mechanism has been try to reason to some point, then shut down and physically get away from him.  

 I am living with someone with a double whammy of ADD and raised in a physically  abusive/alcoholic  household which is creating additional problems re: perspective ( i.e you think this is bad....what are you a princess raised in Mayberry?) He has been medicated and in counseling for years but definitely self medicates with alcohol. Maybe this is just hopeless and I should move on.  

I have been with DH for 15 yrs and have a 5 yr old son. He is a good dad in a lot of ways but I am miserable living in the environment of constant blame and anger and exhausted with having to shoulder more than a fair share of family responsibility (sole bread winner,housework, financial planning/ bill paying etc.). He is very vindictive and separating would not be easy but I am not feeling there is much in this relationship for me anymore beyond not splitting up the family for my son.  However, my son's behavior is staring to mimic the "everything is my fault" stream his dad lays out and I am worried about what lays ahead as I am pretty miserable now and can't imagine what its going to be like if they are both ganging up on me for  unreasonable things that are totally not my fault or responsibility  ( as in  I did not touch your keys/  wallet / do not know where the peanut butter /shoes etc is and please don't call me up at work and yell at me about it!)   

I want to stay with my husband but desperately need to set some boundaries around the behavior and atmosphere of the household or will not be able to keep on keeping on.  

How do I detach myself from his poor behavior when it is in my face nearly every day in the form of blame/anger about something that is usually not my fault/responsibility? Or even if it was a mistake I made, his reactions are extreme such that  'the punishment does not fit the crime" and I am constantly being brought down/aggrovated. He  has zero tolerance for any mistakes I may make yet does not recognize the hardships endured on my end due to his ADD behaviors what so ever.  He blames the extent of our conflict  on  Venus/Mars type communication issues or accuses me of being hormonal.

​How do you navigate this without being a doormat or engaging in conflict?  I am seeing my son start to mimic the bullying/manipulative behavior of his dad and am frankly feeling devastated/hopeless and am feeling very out of patience. I do not want my son growing up to believe if you are loud and annoying/intimidating  enough you will get your way vs. using good conflict resolution /negotiating skills.  But I feel the ADD adds a Twilight zone aspect to this and I am either engaging in conflict to argue the reality of a situation  or  backing down to unreasonable behavior to avoid conflict and feel neither is a good example.

I am out of ideas and patience, have a startle response when spouse walks in to room and other stress related physical symptoms and am looking for some help in getting to the other side of this.