Is it obligatory for the questioner to veil herself from her paternal uncle after she harbored doubts about his gazes, and when does the ruling of veiling from him cease?

Your uncle's gazes and smile do not indicate suspicion that would necessitate treating him as a stranger and veiling from him. The matter seems to be an illusion, especially since you are prone to obsessive thoughts. Your relationship with your uncle remains on its original premise of dealing with a mahram, especially since he is pious. Turn away from these thoughts and misgivings.