Hi Georges.
My dd is now 20 and has her own place to live.She left home just after her 17th birthday and i can tell you there was very little peace in our home from around 15yrs until the day she left.
looking back now I can see that the arguments i used to engage in with dd were often circular and lead us no where. Often my dd would often nit-pick at everyone until she got the response she wanted and her chance to walk out and her excuse to leave. It is better not to engage in these senseless arguments Georges. I think your therapist and dh are right. This continual emotional rollercoaster takes so much out of us im not suprised you are feeling depressed and powerless but believe me you are showing more power and self control by not responding to the name calling and other bad behaviours the way your dd expects.Eventually your dd will realise that that behaviour wont reward her with the response she is looking for.
I know that When my dd is dysregulated it is no good me to try to get my point across or Justify, Argue, Defend, or Explain (JADE) anything she has already "lost it" at that point, her mind is fixed, and just isnt listening at that point. It is better to return to the issue when she is calm and for you to state this in a clam voice.
This is probably drive your dd wild the first few times, and she will probably up her behaviour to get that response but persist with it Georges and eventually she will get it.
Also it is important to take care of yourself Georges. Maybe go for a walk, meet with friends, have a night out with dh, etc. youll be suprised how the smallest thing can make a difference.