I am so sorry for the loss of your husband. I can't imagine the pain you are going through. Honestly, and this is just my opinion, I would not put a otherwise healthy 4yr old dog to sleep. Has the tail been addressed by a vet? I know often times it can be amputated and that solves the problem. I'm not sure how much it costs, but maybe your vet can come up with a payment plan or something? If you can't get his tail taken care of, please, please, please, surrender him to a Bulldog rescue. It is the kindest thing you could do for him. There are many out there, I just google your area and came up with this one bulldog.rescueme.org/Florida.
This must be the hardest thing for you to have to think about and I'm so sorry you are, please consider rescue if you cannot keep him. We have a rescue that his family was unable to care for him and I can promise you, he is loved every day of his life. Maybe you can take comfort in knowing there is someone out there that can offer that for your boy. I really think putting him to sleep will break your heart more than anything. Feel free to PM me or just continue to vent/talk all you want. we are here to help you though this terrible time.