Congratulations on the baby!
Absolutely you must stop this guy, you already have the cult wedge in your marriage to some degree and now this guy on top of that?!
If he doesn't back off simply write a letter to NY and explain in the nicest way that you find it completely inappropriate for him to be constantly contacting your wife.......Use the headship thing for all it's worth! Tell them how unchristian you find it for another man to be so involved with another man's wife on such a regular basis...... Get started now if you want to do Christmas. Then you can have a lovely holiday with your new little one and beautiful wife.
Sounds like he kind of has the hots for her to me and feels he can or will protect her from you.
Over the years and reading all the elder stories it seems to me that some weird elders have a 'harem' mentality when it comes to the women. They (the elder) becomes the 'headship' for the poor sisters with ubm's. They like the power it gives them to be able to micromanage and have control over these brainwashed women who fear reprisal from the higher ups.