Kog
This is what concerns me:
''He is willing to give up being a witness for me''.
I would highly, highly recommend for your sake that you don't let anyone make such a decision "for you". And I'll tell you why. If he doesn't make the decision for himself, then it's very possible that he could resent you for it later. What if things don't work out later? "I gave up my life for you!" he could say. If he makes such a huge, life-changing decision for you, as he says, might it some day seem like you owe him?
And think further... what if you do get married and begin to think about children seriously? Marriage and children are big responsibilities for anyone. For any man, often (hopefully), he begins to shoulder responsibility for many things, the safety of his family primarily, innately, both materially and spiritually. That is a time when many people look to the future. It's very possible that he could begin to re-consider the JW religion at that time.
I would suggest backing off for a time at least. You're both young and you have time, though I know it may sometimes seem like you don't. If he is going to leave the religion, he needs to do it completely on his own terms. He needs to do some study into the religion more than he has if he says he's not much a JW because "he's not much of a fan of meetings, service, and assmblies". That's not enough, though it may be a start.
If he's going to leave, it would be best that he does so because he knows it's not "The Truth", in his heart, and not for you. I think it would be in your interest that he does as well.
And then, if the love that the two of you have for each other is Real, you will be together and won't have such a huge barrier between you.