Have you tried using Nonviolence Resistance with your teen?

My son is 14 yrs and has over the past couple of months become really violent especially towards me. He threatened to stab me in the face with scissors before getting on the roof of our house saying he was going to jump. The police came and spend 90 minutes talking him down. He was arrested for affray simply to keep him safe in custody over night. The police were absolutely amazing with him and I have nothing but praise for them. We are in the middle of a Social Services referral which will hopefully get us more help which the police instigated for us. DS saw CAMHS from Nov '17 to May '18 and again had a one off session last week but he refused to talk about anything.

A couple of days ago DS said he was going to stab me with a knife he had taken from the dishwasher. We thought we had all the knives and scissors locked away but had obviously missed one. CAMHS had suggested using NVR as a way to help manage him so Hubby and I did a sit-in in his room for 2 hours which kind of worked. He calmed down a bit but it wasn't really until he has spoken to our older son that he really calmed down.

I'm wondering if anyone else has used NVR with a violent teen and what you thought of it or if you have any tips that can help us manage this.

Thank you in advance