Why do you have to leave your dog? Why can't you take the dog with you?
If your relationship has 'died" what's the point of continuing the pain? If it cannot be saved, why extend the pain?
Have you tried couples counseling? Do you WANT to save the relationship? If you do, get into counseling and do it soon. There's a possibility that you CAN save it if you both want to. Otherwise, grab the dog and leave. Keeping the both of you in pain is nonsense.
I wish you the very best. God bless and please take care. Hugs, Lee