I did not get to read all the responses. Your scenario, is though, virtually identical to what happened in my family, if you are interested.
My brother, also a Jw fringe-dweller, married Candice. He told me later, and probably told her too, that he always knew at some point he would become a Jw. In his mid-30's he did become a Jw. An extremely zealous and over-the-top Jw. In short, he became like me, his brother who had chosen to take up Jwism far earlier in life.
I believe that in many cases, those children of Jw parents [or similar influences] who don't take on the Jw lifestyle until later in life [i.e.; they fornicate, marry 'worldly people', smoke pot, grow facial hair, etc] become almost monstrous in their approach to the religion due to a desire to "show Jehovah' that I am now serious". This is what happened with my brother. He forbad his wife and children [his wife and one of his children were never Jw's - hated the religion in fact] any holidays inside his home. There were no birthday celebrations, no Christmas celebrations, no cigarrettes smoked, no swearing allowed. I am sure that sexual practices outside the Jw accepted ones were over at that point. My brother became a dictator of 'theocratic' rules and regulations as issued by the Governing Body. He became the absolute head of his house, as all Jw husbands are expected to do.
I recall one time when he and I were discussing our sister who had left the religion several years before. He kept insisting that we, as active Jw's, should take it upon ourselves to 'treat her like she is disfellowshipped', since she was not acting like a Jw anymore. He wanted us to mutually cut her off from our lives. I believe he would have 'turned her in' if he thought that justice would be done that way. That is how twisted the thinking becomes - to the point that one does not retain any idea of personal liberty and freedom - only the cults ideologies matter anymore. Individualism is a hateful idea to Jehovah's witnesses. Anyone not living a Jw uniformity is 'Satanic, evil'. All energy and efforts toward that person is with the idea of 'saving them' from Armageddon, and that can only be done by bringing them into the 'truth' as one of Jehovah's witnesses. If that is not possible, then the bringing of Jwism into their lives as much as possible is what they often do.
Both toward his wife, and toward his sister, and in matters I have not touched upon here, toward his mother whom he alienated until his death due to her failure to live like a Jw. It's almost like a form of mental illness. Nothing else but jw thinking matters to them.
This may not happen to your man. But you need to know that it is a real danger. It might.
My brother was not a bad guy. But he was crippled by Watchtower theology to the point that he could not accept or understand anything outside of that thinking. If anyone had told him that he would do such things, that he would think that way later, he would have blown pot smoke in your face and offered you a beer, saying you had no idea what he was like.
To make a long one short - his marriage did not last too many years after that. His wife could not take the crap he did. She did not have the right to do her own thing. My brother from her standpoint, made life unbearable. She did not leave because of him. SHe left because of his religious zeal. On the day we buried him, she cried her eyes out. She loved him as much as any woman I ever knew loved a man. But her life was turned inside out by his demanding nature, brought on by his demanding religion. He tried to 'make up' to God for all his shortcomings by following the 'letter of the law', which was of course really just the letter of the Watchtower.
My brother is now gone. I feel a bit badly speaking of him in this way. He was a very good soul. But now matter how good, one who falls under the mind control of this cult will act as this cult expects one to act.
Your life will be severly affected if he becomes a Jw - especially I suspect if he becomes one early in life.
Just my two cents. Welcome.