Despite his good qualities, the fact that he wants to continue on with you in secret is evidence enough that he is not an honest man and he is very immature and cowardly (at least in this area). At this point he is incapable of being honest with himself let alone being honest enough with you, for you to invest any more time in him.
He has been lying to his family and everyone he knows, so why wouldn't it be logical to conclude that he's lying to you about his feelings and his intent? In order for JW's to be JW's and believe the doctrines that they know are nonsense, they have to learn how to lie to themselves. To survive on a physiological level, they must become adept at denying any reality that conflicts with what they've been programmed to believe. They don't even know they are doing it.
Hard as it may be at first, you've saved yourself missed opportunities with someone else and a lot of heartache down the road. Even if he were to suddenly come clean with his family tomorrow, I'd stay away from him until he has lived a good long stretch as a out of the closet non JW . It will take some time for him to find out who he really is, once he leaves. One of the things he may discover in the process, is his understanding of what constitutes a good relationship. You don't want to end up being the one who helps him make the transition out of the JW's only to find out that the growth he's experienced has moved him away from you.