>>> Is there by any chance, a friend or love interest who may be influencing him?
He claims that he was convinced of BOM being true before he met his mormon girlfriend. But he is surely blinded by her influence, even though he denies it.
His girlfriend’s father is the local LDS bishop... which doesn’t help things much. He obviously has more influence over him than I do. He asks them (girlfriends parents) questions, but will not consult us.
If your son has hopes of a future with this girl, he will HAVE to convert to mormonism or be dropped like a hot potato.
If he DOES convert, prepare for you, your wife, his siblings, aunts, uncles and grandparents to be excluded from attending his wedding in the LDS temple unless they are "worthy" mormons. You will all be forced to wait either outside or in a "Non-holy" room so that you can all post for wedding pictures on the steps of the temple.
I will pray for you and your family.
(See my post above.)