Being in any long term relationship is damn hard, especially when said relationship starts when you are teenagers. I cannot emphasize enough to you just how much you and your boyfriend will change as you mature. I was a completely different person at 18 than I was at 21 and am really unrecognizable to my old selves at 46. I met my wife at 29 and she was 24 and we had a torrid 10+ times a day type sex life for the first 5 years and we were very passionate and in love on every level talking important issues till dawn night after night and then making it through the day on lust-infatuation adrenialine. We were older and had no issues and we still are struggling now 17 years later with the long term relationship. You don't have as good a start already so be preparred for some tough times.
We were high on love and floating through life. We agreed on almost everything, we were commited atheists, had the same politics, loved the same hobbies and movies, books, etc. and we had great conversations along with mutually satisfying sex and wanted to be together all the time. Unfortunately, this euphoria will wear off and you will have to face the cold reality of the long term relationship or you will break up and hopefully do it all again with someone new. These really are your only options, like it or not. Infatuation does wear off. I'm sorry, but this is a fact. Long term love is completely different from lust-love and that is where the hard work becomes a routine as every imperfection you never saw before in your lust-blinded state starts to grate on you like sand paper. The great sex will become less frequent, bad breath and B.O. will become ever more noticable, the sloppy habits and self doubts will surface, every minor disagreement is a potential battle (not to mention getting old and fat). I cannot tell you enough that this WILL happen, it happens to everybody even if they get a great start.
If you have major issues from the start then you are in for a world of hurt. Your boyfriend being a JW is a major issue. This JW issue will cause you extra grief every step of the way on top of all the normal problems couples have. Your JW boyfriend is also a problem since he is not even a "good" JW to begin with. This shows a real lack of maturity and self confidence on his part. If he lies to his parents and religious authorities then he will lie to you. If he commited to being a real JW or was commited to being an ex-JW then I might think your chances were better but since you don't have a real burning desire to become a committed JW and he obviously has commitment issues, you will have problems.
Bringing children into this is a whole other painful subject. Having children with a good relationship is hard enough. Just wait til you get to balance all this with job stress and money problems.
At this point, he just is not worth it. Young lovers have to make their own mistakes but please think hard about what everyone has said and take advantage of some experiance to save yourself a lot of pain.