It's going to be hard not to charge in but you could just stick to the lack of love & as you pointed out the controlling, willing to destroy your marriage behaviour of your respective families. As always JW facts, CofC Ray Franze , pm if u need the download as they have passed away with no kids its free now.
The Searcher on this site has really the best SCRIPTUAL quotes for those questioning from a Biblical perspective. I would seriously recommend his stuff for an unsure Christian.
Really hope this works out for you both. It stinks that the in laws where willing to split you up. You I know will be the bigger more loving one toward them as u know its their cult selves behaving in such a cruel way.
xxxxxx sister D