I'm planning to expose my ex-boyfriend as a fake.
Why do you want to expose him as a fake?
He is always trying to brag about his job but he only works in the mailroom.
You are not with your ex any more and what he does and says is not your business to get into. Getting involved with his actions is not correct. Stay away from him.
I'm going to make him pay for what he did to me.
It is healthier to just let things go. He'll get what he deserves eventually so you should just focus on your life right now.