My suggestion is to move on in your life and forget him. I know that is harsh, but you need to face reality. He is very conflicted between his beliefs and his feelings for you, but he needs to pick one and commit, otherwise there is no future for you, he is doing you a disservice by holding out hope of a possible relationship, it's cruel. The problem is that this is not a normal religion, it is a cult. They keep people tied up in these feelings of fear, obligation and guilt, it's really difficult to get them to make rational, independent decisions.
Even if he did marry you your life would forever revolve around his beliefs. You may think you could work with that, but it will get old. He will be looked down on for having married outside "the truth", you will be considered less than by everyone he knows. What happens when you have children? Do you want them going to the kingdom hall to be told everyone but Jehovah's Witnesses will die soon at Armageddon? Trust me, he will feel an obligation to teach them these things. Do you want to celebrate Christmas, birthdays and other holidays by yourself? This is the reality of life as an "unbelieving mate".