The thing that strikes me about this is--why is your ex actually PAYING for information about your life? That is not normal.

It seems like there is a lot of one-sidedness in your relationships both with your ex and oldest son and when you are being betrayed it's hard to know how to handle the situation. It seems like both your ex and your oldest son do not have much concern for how they make you feel. So my thought is, have you actually told your oldest son how it made you feel that he was doing this stuff behind your back?