For your child, you must show that you're happy and that you don't feel you have "lost" something. Be sure that, when he is with you, that you are happy and he is having a good time. Kids remember how they felt much more than what they're told or indoctrinated with.
Your child will not be allowed to have "worldly" friends by his mom. That is where you come in. You need to plan fun activities for him and his friends at school, and/or children of your co-workers. If he is in elementary school, and you have the free time, it would be an excellent idea to volunteer as a room parent. Room parents (used to always be room mothers) plan holiday activities and go to school to supervise holiday parties and similar activities. If your wife objects to birthday parties, you could have "unbirthday" parties. We all have more "unbirthdays," so it gives you flexibility.
Encourage your child to do well in school, and help with homework. It is important that the child feel secure and supported by you.
As "head of the household," you have a distinct advantage. But, as jgnat pointed out, it is important to be loving, kind, and understanding with your wife. You once believed as she did, so you give her that freedom. If she needs a ride to the meeting or field service, give that to her.
Nobody knows what will happen, but I think if you follow all of the advice you've been given here, you'll greatly increase your odds of keeping your family together.
If you could move to another town or another state, that would take off a LOT of the tension of fading.
Best wishes.