Are the mentioned ghusl from blood and rinsing sufficient to remove impurity, and is what I doubt about remaining traces of a face mask excused in ablution?

These are obsessive thoughts, so you must ignore them. A small amount of blood is removed by pouring water over it, and a small amount of blood is among theesses that are forgiven. It appears that the mask was removed by water. It is permissible to adopt the view of those who consider a small barrier forgiven, and it is permissible for the one afflicted with obsessive thoughts to adopt the easiest opinions to alleviate hardship.