I think you sound needy and insecure. If your fiancee is into this guy and wants to cheat with him, there is nothing you can do. So you have to have a certain level of trust that she handles her work relationships in appropriate ways.

Has she ever given you reason to suspect she would be unfaithful? Is she usually clear and open about her relationships or friendships with other people, people that probably include men?

Even if the guy has an ulterior motive for lunch, or for asking for a playlist then you have to trust her to handle it. Just because HE is being 'inappropriate' doesn't mean she will be.

The other things, I really think you are overreacting.