Welcome to our nightmare
I was like your BF, but I was unbaptised (thank God). I got out because I didn't like the control and did not agree with some of the rules, but I still wasn't free of the cult.
I married a nice Anglican girl. Now. She is the JW, our kids are JW, and I am the bad guy because I have now done what I was discouraged from doing from birth and put the religion under the microscope and discovered a whole range of nasties I either didn't know about, or had suppressed.
Until such time as child of any high control group fully understands that their leadership is not being directed by God/Christ/spacemen/whatever, they are damaged goods and are not marriageable material.
The Watchtower's primary doctrine is that Jesus selected the WT in 1919 to be God's sole channel of communication to mankind in our day. As long as he believes that, your BF is under full blown mind control, even if it doesn't show in his actions. JWs that look 'weak' or are drifting are often concealing deep seated guilt. This is how I was.
You are in a position to have your BF and his family and not join their church, and not have all of the mind control crap that goes with it, but it is not easy and if you put one foot wrong, you could waste your efforts.
You have to get them to realise that the above doctrine is BS with setting off their alarm bells.
You must not tell them it is BS.
You must not tell them why it is BS.
You must not tell them that you have been visiting apostate website, or reading apostate material because they might run away.
You have to do it solely by asking questions and not letting them change the subject, attack your character, talk volumes about closely related subjects without actually answering your question, a whole raft of cunning ways of getting around confronting issues they don't want to face head on.
They are not hard questions to remember, but you must get them right because they will squirm through the tiniest loophole and you need to start again.
If you are not able to take control of the conversation, or walk away from it when it is neccessary, you might not be able to do it.
Do you want to try??
Chris