I hired a contractor to do some ceiling and door repairs in my home. He completed some of the repairs, with me telling him throughout that I was not satisfied with the quality of the workmanship...but he kept going ahead. I have paid him about 60% of the original contracted amount. At this point, the workmanship is so poor, and the contractor so aggressive and obnoxious, that we've both agreed he is to no longer do any work in the home and he has vacated. However, he still thinks (according to his calculations) I should pay him another $440. I disagree, but in the interest of getting it over with, suggested splitting the difference. That was acceptable to him -- except now he wants me to sign a waiver stating that I will post no negative comments on review sites or social media or I will open myself up to legal action. I have no plans to proactively post anything, but I am leery of signing this letter. He's saying he won't agree unless I do. At this point, I just want to tell him no, and not give him anything else. Does he have any grounds for legal action against me?