Advice on Barking?

Hi,

I have a JackChi that I adopted when he was younger, he's always been ver reactive around both people & other dogs. With a *lot* of work & help from a behaviourist we've managed to decrease his reactivity around humans massively and we are continuing to work on this.

So the reason I'm posting is that when we are at home he will bark at any & every sound. Car driving past? Bark. Wind? Bark. Our cats walking around upstairs? Bark. People walking past outside? especially bark. We've tried all sorts- trying to distract him, treating him when he is quiet, having the tv on constantly, even telling him off when he does bark (but it felt awful). It's been 2 years of him going bark crazy over every little thing & of us never being able to settle because we're trying to stop him. I would really really love to be able to sit with my dog and him not explode at every single sound. Please can anyone advise me.

Side note: Im not expecting him to be quiet constantly, I understand if the door goes etc I don't blame him for getting uppity.