When your child wants you to leave, that speaks volumes! Poor kid!
I would like to second what LisaRose suggested, that you try counseling if you want to try and stay. I would try to do it as a family first, reminding your husband that he is the one who changed the rules. When you met & married him, he was not an active witness, then after comitting adultery, he decided to be a "good boy" and do the witness route, apparently forcing you and your child to do likewise, whether you wanted to or not. He owes you that much. If he won't, and he continues with this emotional abuse, yes, please get your ducks in a row, and prepare to leave for your child's sake as well as your own. Talk to an attorney w/o anyone knowing before you do anything (except perhaps squirreling away some safe money). You have to protect yourself and your child.
Use information from jwfacts along with the wt mags to show your husband the dishonesty of the wt.
Scully made some very good suggestions. If you're close to any of your family, maybe they could assist you with keeping some things at their place should you need to. But definately speak to an attorney before you do anything. Talk to a couple to make sure you get a good one. Many talk to you the first time for free. Be discreet until you have made decisions. Protect yourself and your child.
All the best to you.