Dear Mum Chris~
First off I'm glad the danger is no longer present, if I understand matters correctly that was your son, who was let out on bail. I'd imagine in time without that constant threat there will be a big difference in how you feel.
Yes it is sad part of your family is lost, however that was their choice by devaluing you, threatening you and behaving in a toxic manner, not much consolation I know. We don't always have a choice in how children behave.
Secondly and maybe more importantly you were not fooling yourself, it was a genuine and big improvement, a significant thing - and that ability is still in you, then and now; even if you retreated for a while - which happens.
As far as not standing up in the dangerous situation and getting help from police or others I think you are expecting far too much from yourself, and that is at least partly lack of experience of how others react."a coward weak as piss" is utter rubbish.
I was a policeman and can assure you that most "healthy" people threatened, either by family or strangers, will go though exactly what you did, with being unable to breath and virtually paralyzed -voiceless. It may not seem very glamorous but is natural and very often the best thing to do. The same applies with being bullied.
People even go though exactly the same when coming home to find there has been a burglar there .
It is only later, perhaps with support of others, that sometimes action can be taken.
It may sound hard but try to give yourself some slack, things have been terrible and that makes a huge difference.
!800RESPECT may well be able to assist you in your loss and grief, or point to to someone who can. Going it alone and being strong for others may not be the easiest way to do things.
You may find something in common with the parents on this thread, which is long, but includes many people in related situations:
I'm hoping you will now have a chance to start to feel better and more in control