Satan cannot win against the Holy Spirit. Satan and the HS cannot both be in the same body. Any possessed people are not saved people.
You don’t have to be possessed to get hammered by Satan. The entire purpose of exorcism boils down to that final decision - to choose Christ or acquiece to possession. They all end that way. You are correct.
My point is that REGARDLESS of your being saved, your BODY is still fair game. So is that of your family.
There are degrees of possession as well. There are partially possessed and perfectly possessed people. The perfect seem to be beyond the help of an exorcist.
Christians are the second most persecuted religion on earth, second only to Judaism (makes sense, right?). That’s not an accident.