ADHD ADULT SON ENGAGING IN TRANSFERENCE

I divorced the emotionally, physically, mentally, spiritually abusive father of my children in 1980.  My son is age 42, daughter age 41and I am 65.  I raised the children w/o the help of the father.  His involvement in their life was almost nil.  He began an entrance into their lives when my daughter married in 1993.  This is a very complicated story, but I am going to attempt to make capsulize it.  My son has ADHD.  His Father was very rough with him and he told me that I was to blame for not disciplining my son.  My son was a challenge in all phases of his life.  As an adult he has caused me much consternation and challenges.  I know now that I made mistakes in helping him as much as I did, i.e. financially.  However, one never wants to give up on one's children.  So, time marched on and he was abusive to me and I would then get him out of my life.  Then he would act better.  Then he would regress.  I never gave up on him.  However I was not good at setting boundaries as he always found a way to break them down.  And I am not good at boundaries anyway.  I managed to become a stockbroker and have a successful career as a manager for 11 years.  Then the stress of my son and the lack of support from the father, paved the way for my becoming ill with CFS.  As time marched on, my son would be appreciative and decent, and then regress and do unacceptable things to me.  I would always distant myself and stay away.  SO, today I am writing because my son is practicing transference (and has for 2 decades) of his hate for his father to me.  He talks abusively to me at will.  He does not seem to be able to control his emotions toward ME.  He has for some time now, been in an attention getting, sucking up mode to his father.  They are good friends now.  I am NOT unhappy that his father and he have reconciled.  In fact, I had a part in that happening.  However I am devastated that he treats me with horrible disrespect.  There does not seem to be anything I can do to make this better.  Any approach I take with him ends up being the wrong one.  I can act very polite and nice and he abuses that.  I can raise my voice and match his mood and that does not work either.  As in Freud's explanation of transference, he has taken the role of the abuser (his father) over and is perpetrating it upon me.  I have a situation now where I did something nice for him, got him an antique from his uncle in MT, and he was to give my brother something in return.  One and 1/2 years later, he has not held up the bargain and my brother is NOT TALKING to me now.  In order for my brother to again talk to me, I would have to spend $200 and fulfill my son's obligation.  This will pacify my brother, but is wrong action for son (no behaviour modication here).  I do not know what to do.  Also, I am absolutely ready to disinherit my son.  He was rude to me recently about Christmas gifts.  I called and his new wife was not home, so I spoke with her son and asked what he might like for Christmas.  My son (and his wife) called me at a stressful time, they did not care, and they 'told me off' for doing this.  He argues incessantly.  He says to me before I can even speak, 'stop stop stop stop stop stop' and then I interrupted him and I did the same to make him quit.  It went no where.  He find things to be abusive about.  Is there any hope to fend off the transference or should I set our relationship aside and live my life without him?  Also, should I give my brother the obligation or now?  I need to say that I am a kind, compassionate, caring, responsible person and people like me.  My life is absolutely HELL with this being unresolved and no seeming answer.  Thanks much for any help.