I am sorry that you are having this trouble. There may not be any government program to assist you, but you can go to www.benefitscheckup.organd check on their comprehensive data base to see if there is any thing for you. It will take you 20 or 30 minutes to go through this site, but you have to do it because you are the one with the information.
Your best chance for help may be to work at the local level . Can you go in person to tell another the trouble you are having. Ask for help!
There may be local groups or non profit organizations to help in special ways. Start with the area agency on aging. I would call them, tell them your situation and then ask who you could speak with.
Also, I would call your nearest senior center and ask for people or organizations to help. It seems as if the plumber should stand behind his work so that you don't have to pay over and over. I can only guess at this, since I don't have all of the information.
Also, your church may have groups that serve elders. If you are a member of a church, don't be shy about asking for help.
I can hear your frustration in the way you write. Somehow, I feel that your need and your clarity, if expressed in person, will bring some help to get this problem resolved.