If I were to be honest your husband is like a lodger in the home using it as the base for his activities but without an emotional connection to the people within it.
You are distanced from one another because the religion itself makes marriage relationships unnatural placing themselves between the couple. Men are encouraged to keep secrets from their wives and to strive for position which will inevitably mean putting wives and children second.
You do not share a common religious belief and whereas you may be able to accept his differences he will never accept yours. As an unbelieving mate he is taught to be ever suspicious of your motives, your sources of information and your character. It is hard to have a stable marriage or close relationship under these circumstances.
He has shown he does not believe himself to be in a committed relationship by his emotional philandering. Calling another woman your best friend and forming relationships with women to whom you are not married is what you do when you are single.He has lost your trust and any man who still loves and respects his wife would be working to get that trust back. He seems very casual about the whole thing with little care or concern for your feelings.
He is using you because you provide the means for him to attend college and you take care of the bills. When he completes his degree and his work improves and he does not need you to pay the bills what is there in the relationship to keep him with you?
If you want an unpaying lodger then do nothing. If you want to be in a relationship then these issues need to be addressed.