Do you have any friends who could take him for awhile, maybe someone with a farm and other large dogs? Sounds like he needs a change of scenery.
I have a similar scenario with my dog who lost his boon companion last year and has mourned her ever since. He changed all his normal habits and...
Seeing as the third option was the only one that had "put him down", it left little options for that choice, don't you think? Personally his behavior doesn't lead me to believe he would kill livestock. I chose that option because the OP clearly has given this a lot of thought, has tried...
I keep my dogs until they leave this earth also, so I can sympathize. I also would give one of them the hand of mercy if they were suffering(have done so) or couldn't be broken of destructive behaviors(have done so) before I would inflict them on an already glutted shelter system.
I voted to...