So sorry to hear you are still having probs with Jarvis, I've been through it with Ben in the past.
Don't know if this applies not
but it took a behaviourist to point out that I was triggering and escalating some of Bens behaviours unknowingly. I used to tense up if children or dogs or anything I though might start him off 'on one' came too close, as I knew what he was capable of doing, and he took this as a cue to get more wound up.
The more anxious I got, the worse he was
I know you are a more experienced dog owner than I was when we had Ben, so you are probably more 'sorted' than I was and I am sure you are already aware of this, but I do know I used to anticipate his behaviour and things are much much better now I've taken a step back.
I do hope you can get some help and get sorted, its not much fun is it when you feel on your guard all the time, especially when you know what a lovely dog he can be
and what sort of relationship you can have.
Bens mum