he lets them watch LOTR
What? I don't think that's appropriate for first and second graders. Those films are rated PG-13, as I recall, because of all the Armageddon-like battle scenes. It's not that they aren't good movies, they are. But they're for teens and adults--not young children. Remember that custody decisions are based on what is in "the best interests of the children", so this apparent lack of judgement may be relevant in a custody case. Your attorney should know that your Ex allows this; a lawyer will know whether the court would consider that when making a decision.
When dealing with the children, I agree with Heartbreaker. Be a good and loving parent, don't disparage their other parent (even if he does deserve it!). You are your kids' primary example of what a non-JW is. Don't make the WT propaganda come true; show them an example of a good person who doesn't blindly obey every whim of the F&D Slave-drivers. Keep the long-term goals in mind, that will help you have the courage to act honorably and persevere through the day to day battles with your Ex.
Wishing you and the children the best,
GLT