H angry at our son

2 years ago, h got into a physical fight with our adult-aged child.  H started the fight, and started the physical aspect.  H is nearly entirely at fault.   H ended up with a black eye.


I was the only witness.   over the last two years, H has "changed " the story painting himself as a total victim..   He has not seen or spoken to our son since.   One therapist did tell him that "as the father", he is more responsible since he should taken steps to prevent.   


H's current T is telling him to write a letter to our son.  H has written two letters, but both have been deemed unacceptable to his T.   H has been vague as to what her complaints have been, but I suspect that it's because a T knows that it is likely HIS fault that the fight happened, and that H's letter has not been mature (taking responsibility)


Anyway.....all of this letter writing business is making H relive the incident and he blames me .   Now, every couple of days, he has been blowing up over minor things, and then yelling at me over the incident with our son.


I don't know what to do?