First of all, it was a good move to not go. If you don't show up, you will avoid having to come up with the material and illustrations for the talk. Which is a difficult thing to come up with, since you are supposed to dig through the littera-trash of recent vintages and find the stock illustration they want you to use. Plus, there is no way of knowing with certainty if they are even telling anything that resembles the truth about God and the nations' frustrating His purposes. If you don't go, you not only avoid the work but the moral dilemma of supporting a lie.
Now the hard part. This is why they want people to marry only in the "Lord". That way, if you decide it's not for you or that it's a lie, your spouse will keep giving you a hard time about going to the boasting sessions and you will have more to lose should you disassociate or get busted and disfellowshipped (which sounds like it's only a matter of time before it happens). You will need to be gentle yet honest to your husband about your true feelings. I expect him to be irrational and fly off the handle, and try to guilt you into going back when you tell him. You will probably be getting lots of visits from Brother Hounder about that time (at which time, you will probably find it necessary to write up that disassociation letter or get busted for something).
However, it is usually better to tell him honestly that you have serious reservations about the cancer, and that it is doubtful that you can go back to being a witless. If you try to hide it, you will eventually be found out anyway, and then you will have the trust issue on top of the fact that he is not accepting that you no longer want to be a witless. And the trust issue is more likely to bust up the marriage than the religion issue. He might become suspicious that you are doing other things if you are not honest about this issue, and then the sxxx is going to hit the fan.
One can only hope that the worst that will happen is that he will continue to serve his God and let you drop out quietly. If you have no children and your parents were not in the cancer, the worst that can happen if you get disfellowshipped is that you will lose the "support" (=hounding) from the congregation. Even if he remains faithful to the cancer, getting disfellowshipped will not bust up the marriage now. He will go to his boasting sessions, waste time in field circus, and live a stagnant life while you are free to study whatever you feel like, sleep in, and watch whatever TV or music you want. Of course, you will likely find littera-trash where you do not expect, and will probably be hounded to go to the boasting sessions.
If it becomes a physical abuse issue, then he has stepped beyond the line. At that point, it is best to report it to the police. Besides a nasty embarrassment to the congregation (for which he might himself get disfellowshipped), it will impression him that physical abuse will not be tolerated. Even strong emotional abuse (strong insults, the extreme guilt trips, etc.) could result in some kind of harassment charges (or at the very least some embarrassment for the congregation).
All in all, your rights stand. You are not responsible for what your husband decides to do, especially if you no longer feel it's right. Once you honestly tell him that you no longer believe in the witlesses, your responsibility ends. At which point, he will have to either accept it, do his own research and find out what led you into not believing, or risk further disruption in the marriage (which, as cruel as it might sound, might be better off busted up early than bumbling on for decades of fighting and abuse), You are best off standing up for your rights, even if someone's feelings are hurt. And, even if it means missing all those boasting sessions. Even if it means missing the Crapmorial.