Manager or just man

New hire has really good experience in the field that my fiancé works. Plays it off as the quiet but intelligent new guy that keeps to himself. Time goes on and he's really been putting his best foot foward as him and my fiancé work as a good team. He gets a promotion. Shit hits the emotional barrier fan. My fiancé wants him as a good friend but his work ethic now has inconsistencies that spill into personal life (messing with employees schedule for his days off, no longer working hard with the team). Im trying to be good and let them be friends. We're invited over for dinner and I adore his wife. In the past week or so his team and himself have messed with procedures that are to be done by my department alone and directly affect his work. For being 'such a good guy' and 'kind and thoughtful', I never thought I would be attacked for coming over and help to fix my departments procedures that he fucked up. I was miffed and went on with life. Few days pass and I need my fiancé to get some days off so we can travel for family. I ask the manager above this guy to do it and he does. Low and behold on todays date, the guy then comes to my department to cuss me out for taking away 'his best worker' on the days that he needs off for 'reasons'. He then proceeds to tell me that he went behind his managers back and changed the schedule again. The end of my shift today, im balling my eyes out to my fiancé and hes trying to comfort me the best he can and telling me that he will only play nice till the higher manager signs the papers and my fiancé becomes higher than him. I dont know what made him start in on me like this but its getting progressively worse and worse. It all started after my fiancé told me that when he was first hired he was messing with the female in the department behind closed doors. Since that woman moved away his new prey has since been behind the closed door too. This is the reason he needs certain days off. How am I supposed to play nice at dinner with them when all I can do is look at his wifes gorgeous face, dode over their four kids, and scream internally?