If you do believe it fully, are you not really going to want him to make the conversion ultimately.
Once you both die, you will not be married in the afterlife and she will get assigned to be the polygamous wife of someone else. This also means giving her something specific to do. Unless you have those same understandings, Germaby sad to say the relationship is almost certainly doomed.
Keep your power, girls, and keep the marriage egalitarian.