Is it permissible for the husband's paternal uncle and the husband's brother to see the woman without a head covering, and is it permissible for the husband's mother's husband to live with her in the same house?

Your husband's paternal uncle, your husband's brother, and your husband's stepfather are non-mahram to you. Therefore, it is not permissible to be in seclusion with them, nor to uncover your hijab in front of them, nor anything else that is permissible between mahrams. As for uncovering the face in front of them, it is based on the difference of opinion among scholars regarding the obligation of covering the face in front of non-mahram men.