I'm not aware of a way to change "All" to some other word(s) in a quick filter.
If the domain of values does not change frequently, consider using a Parameter instead. You can specify any values you want in a Parameter (including whatever you want to use for "All"). Then build a calculated field to compare your original field with the value of the Parameter, taking into account whatever value represents "match everything".
Yes, but with parameters there is no multiple selection and the user need this option.