1. Is there any Bible principle that prohibits somebody in modern day from just "calling the police"?
If you think someone is in your house, going to rob you, does the WT say "You need two witnesses, call Legal Desk, and we'll tell you what to do"?
If you came home, and found your family member murdered, you would call the police.
If someone breaks into a Kingdom Hall, "the first thing you should do is call the police."
There is no rule in the Bible that says you cannot or should not call the police.
There is no rule in the Bible that says elders should disfellowship or shun someone for calling the police.
Robbery is a crime, call the police.
Murder is a crime, call the police.
Child abuse is a crime, call the police.
After that..... after "the superior authorities that you are in subjection to" are notified...... do whatever else you want to do. Want two witness? go for it. Want four? go for it. Do whatever you want to do in your stupid little 'committees' "that God has assigned to you."
Just report the crime...... call the police.