Teen boyr with ADHD and depression

I am the mother of a teenage boy who lives with ADHD and now, suffers from depression.  He is in his first serious (read, sexual) relationship, with a young lady who is not stable and comes from an abusive and neglective background who has a learning disability which adds an immaturtiy level.  We have 5 teenagers in the house, 4 of the boys, me and my husband, we are a blended family with an adopted boy with fetal alcohol syndrom, in addition to my son with the adhd - yes, I figured I could handle it.  Now, that gives you the basics, the adhd doesn't allow my son to deal with the emotional turmoil that an unstable, manipulative girl can dish out.  The rollercoaster ride lends itself to outbursts of first aggression and foul temper, then tears, all misdirected and unreasonable.  The depression causes him to lash out at the two people is closest to, myself and his biological brother.

My son has tried to break up with the girl, which is a good sign.  We are told by the psychologist it could take a few tries.  Right now, he's in love again.

My son will take his meds and acknowledges that they are important, but refuses any more therapy.  The rest of the family does go to therapy so we can deal with him and with the emotions that his temper outbursts put upon us. 

He is vicious, mean, vulgar and verbally abusive, but not a physical threat to himself or anyone else apparently. 

I feel like my son is dead and in his place is this very mean, not nice mentally ill person that I have to try to reshape to find a semblence of my child.  My oldest son, his brother, is now exhibiting his own signs of depression, probably stemming from watching his brother verbally vulgarly abuse his mother and his own girlfriend and want to thrash him but holding back.  Some days it is only by my restraining him.

It is difficult in a house full of testosterone to keep everyone from antagonizing the situation.  I don't like it myself and there are days I think I may have to have him committed to a crisis center if he doesn't settle down soon, but, then he does and I'm left exhausted, hiding my tears in another room.

This has been going on for approx. 5-6 months and I'm hoping the next med works.  I'm not sure what that looks like or what therapy looks like after his moods are stable, but I can't stop trying.