"I have suggested moving locally but DH IS against this as he wants to live far away from all people."
His desire to live far away from all people is a separate issue from these arsehole neighbours. In your OP you listed a whole host of reasons why moving to the country now only works for him and not for anyone else in the family. So no, I would put my foot down and insist that he consider the rest of the family and not just himself. The current problem is one particular family, not the entire world; the solution to this current problem is a local move.
"We have been having issues in our relationship over the past few years because of his anger and my enabling behaviour and I feel like this issue might be crunch time
"
I can't say I was surprised when you subsequently posted this
.
"I agree that his MH is suffering but I do think there is always something which he fixates on. He thinks that moving to the countryside will be the answer to all his problems but I don't agree with him. I think there will always be something he is not happy with. I do think he would move halfway up a mountain if he could." (my bolding)
Thinking something, anything, will solve all your problems; well, it's just totally unrealistic. A little bit childish too. And when he finds that moving to the countryside is not the magical solution - what then? That's a recipe for deep depression.
I think the best solution is for him to accept a local move. It deals with the current problem, but when he's not happy in the new place (I think you know he won't be, regardless of however lovely it is) he will still have his utopian dream of the countryside, which you seem to also want, just not now.
I think he also needs to address his anger issues, and you know you need to stop enabling, but that's a bigger issue altogether.
And if he will not compromise, will not consider the needs of the rest of the family - then yes, crunch time.