I'm so sorry - the frustration and exhaustion you feel is obvious. It's completely understandable that you're at the end of your tether.
Others here have/will give better advice, so I'm mainly adding myself to the sympathy brigade.
But of course I can't keep my mouth shut, even when I don't know what I'm talking about, so take the following with a grain of salt....
I do agree with
@snowbunny about trying something new - though with the understanding that you may feel you HAVE tried everything! Nothing of the intensity of what you have with Bear, but I was feeling very out of sorts with Carbon a few weeks ago. That recall challenge that
@Beanwood posted about was oddly the straw that broke the camel's back with me. It depressed the heck out of me that I've had Carbon for 3 years and he still has zero recall. Every time he ran towards another dog, I got so angry that I couldn't see straight. I felt like there was nothing we did together that we both enjoyed and all I was being was the prison warden keeping him from absconding or chasing after him once he had already absconded.
Before I had my week holiday, I decided to do something different and find something that we both enjoyed. I told myself I don't even think about recall anymore: I simply have a dog who will run away if given the chance. So I don't give him the chance. Or if I do and he runs, then don't get angry because I knew he would do it. Over the week we tried "church parkour" (thanks
@HAH ), went on a boat ride, walked in town (which I know he enjoys from our time in Regensburg). We went surfing in the mornings when no one was around. I always love Carbon, but the shared activities helped me remember why I LIKE him too.
It wasn't perfect, but the side effect was that I'm not getting nearly as angry and frustrated and (no surprise) Carbon seems happier and more relaxed. His anxious tail thumping behaviour (similar but quieter to Bear in the video) is better and - maybe more importantly - doesn't irritate me nearly as much as it did a few weeks ago.
Your issues with Bear are very different, but what I'm taking a very long way of saying is that maybe just chuck out what you've been trying and do some stuff that reminds you of why you like Bear. Or take him out and try to interact with him as if you'd just met him and find out what there is to like about him.
Not sure if any of this even makes sense - bottom line: you're totally justified in feeling the way you do, but you'll come it of this.
