You can get your local instance admins to delete the messages from its DB, but you can't do anything for the other thousand or so federated instances, they all have a copy of the messages.
Safely depends on the content of your messages. But generally, consider your messages public.
"A super AI that is perfect at finding people" - firstly, doesn't exist, secondly, by definition cannot be defeated. Otherwise, use e2ee when possible, and talk in person.
$200 + KFC, don't be greedy.