It seems like you are not as fully in as many were at your age. Now is the time to ease out of it gracefully and your weekend at the convention seems a good enough reason to pull back.
I don't know how your parents (mom and stepdad) are treating your fiance or how they feel about your relationship or what kind of people they are, but please be careful of assuming the worst about your stepdad. Not all JWs are monsters or pedophiles. . . otoh, that your mind went there immediately after learning about the ARC and JW actions in that area does concern me, so please examine yourself to see if it was a knee jerk reflexive response to all the new info about pervy JWs or if there might be something more to it.
Don't let anyone here sour you on your belief generally. We are all kind of cynical on the subject, even when we are believers. You will come to your own conclusions but right now, the organization is the issue.and there is no harm in removing your belief in God from your belief in the org. Fully separating yourself from WT indoctrination will allow you to examine and explore what you truly DO believe, but don't let any of us put you down for it, whatever that might be, whether they are laughing at you for believing at all or if they are trying to get you into their new faith.
Most here are motivated to help. You saw through the org, so now is the time to start trusting yourself generally to evaluate the information you are given and its veracity.
Good luck!!!