Let me go on a limb here. If you two are young and had had a sexual relationship, then you have to be cautious about him. Men at a young age, especially men who have been in sexually repressive cults, could say anything to get laid. So he is fooling himself and you if he claims that he doesn't believe in the religion, but knows nothing bad about it in extensive detail as most of us here do. In this case, when the "honey moon is over" he will revert to the cult mode.
The only way you can be sure that he is out of the religion is if you confirm that he has read the most important anti-JW books (at least three or four) and can tell you everything bad about the religion. You will get this confirmation when you can see that he is genuinely very upset, possibly enraged by his newly acquired knowledge. Then and only then will I start believing he is mentally out.