Oh my god, I hear your anxiety!
Did you find a new job, I hope? Save every single penny you make so you can stand on your own two feet. Move out, that is priority. If they are pressuring you to get baptized this summer, just tell them you aren't ready. How old is your son? He should be safe as long as he lives with his dad and is with them most of the time. Tell him to be polite but not pay too much attention when they start talking about religion to him. When you move out, be honest with this flirty step cousin of yours about how you feel about the religion. I know you feel trapped, but as soon as you move out, you won't be. And they can't make you get baptized. I know you feel guilty because you have to live off them now and they helped you a lot. But that isn't worth them sucking the life out of you. Stay in control.
Much love.