I suggest being 'the nice guys' and NEVER bad mouth his mother, never criticize the JWs and always just give unconditional love and support.
If need be later on you will have to be prepared to FIGHT her to maintain the fantastic 50/50 care.
Amen, Aussie Oz! The last thing you want is to join in the conflict she seems to want. If she ever convinces a judge that your household is defaming the other side, she may get primary, even full custody. Your husband is in an good position having 50/50 custody instead of the every-other-weekend plan--don't jeopardize that. This works both ways, of course: she shouldn't be disrespecting you and your husband, either.
Whatever the adults need to say to each other, they should be saying it directly--not going through an eight year old child. The parents and step-parents should be working together, not against each other. The present situation is bad in so many ways:
- The Ex-wife is pressuring the boy to take sides against his father ("worldly" people make Jehovah sad, do you want to make Jehovah sad?)
- She is teaching him to disrespect his father (and also to disrespect herself, in the long term)
- It sets a bad example of adult behavior, which your stepson is likely to imitate as he grows older (he's already more than half way to puberty and high school)
- He will learn to that it's OK to play both sides against each other, and how to do so effectively
So walk the high road: don't give in to her manipulation, but don't respond in kind either. Insist to her personally that she behave in a manner fitting a responsible, christian adult (if she has to fake that part, it's her problem ). Check into the separation and custody agreement. There's a good chance it includes language about not disparaging the other parent, and may also include language about your stepson's religious upbringing. Tell her she must honor the promises she made and the court declared binding. If she doesn't live up to her responsibilities, get it on the record--phone messages, email, or in writing--so she can't deny her conduct if she runs back to the family court trying to change the custody arrangement.
When he comes back he feels guilty for whatever activities he did with us.. We even tried to sign him up for soccer and his mother went ape#$&@. She doesn't want us to read him books like C.S. Lewis's the Chronicles of Narnia. She doesn't want us to do anything for holidays
That is so one-sided! His outside activities should be by agreement of both parents and based on what is best for the boy, not dictated by one side to score status points with the elders. She says no soccer, but how would she react if you said no Field Service? She says no Chronicles of Narnia, but what would she think if you said no Greatest Teacher or My Book of Bible Stories? She says no to Halloween, Thanksgiving, Christmas, birthdays, etc. but what if your rule was no "Memorial"?
Consistent love and guidance, a model of mature behavior: that is what your stepson needs. Do what you can to give that to him!