Linerunner have just done that to DS's (16) bedroom too, for the exact same reasons. We let him (within reason) choose the colours, furniture and just have to get the accessories. He helped to change the skirting boards and paint the walls and ceiling.
He built his own furniture and worked really hard for 9 hours (I just helped him initially with the bedside cabinet - how to read the instructions and get all the parts organised) Then he built the 4 drawer chest of drawers himself. We heaped lots of praise for his hardwork and there has not been even a sock left on the floor.
This is the second weekend and so far, fingers crossed, we have had calm for almost 2 weeks but the last 3 years have been hell! The moods, temper tantrums - we have had it too.
I have read Maryz's advice and picked up quite a few tips, we only have 2 rule with DS, no phonecalls or letters from school re behaviour - if we do automatic 7 day grounding. And everyone has Sunday dinner together.
I fully agree with the backing off, try not to get drawn into the shouting (it is hard). It will get better, maybe not next week but gradually the length of time between outbursts gets longer.
Also I found that when DS is tired, even if he thinks he is not, then it is/was worse.
Sorry for the rambling post but I found that when I finally admitted to a couple of friends what was happening at home, it was to my emmense relief we were not the only ones. It is more common than you think but everyone does get through it (just not overnight)
Goodluck