Some red flags here.
I think if I were in your put the breaks on right now and re-group. I would be VERY patient, get to the bottom of his feelings, let her know that this is an issue that isn't to do with her so as to make her know she has not done wrong and include her in your conversation with him. Once you get into this kind of relationship there is no "marriage" or "couple" there is three (hence "triad). If this is meant to be more than sex then that has to be very clear if you are to succeed. You will need private times together as two people and he will have to work through his jealousy.
Frankly, I would move her out and get some space. Her living there, you two being married, having three kids there is a recipe for disaster if you ask me. Not the best way to build a healthy triad, but, maybe it will work with a shit load MORE work than usual. Add religion to that and woooooah! More work.
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