I sadly don't have any good advice at this point... It sounds like you, as a family unit, cannot be happy mono OR poly... and breaking it off doesn't seem like an option either!
One thing I don't get though... If you're mono, why are you looking for other women? It seems to me you'd only be making things worse. You don't want to be with someone else. You'd only hurt yourself and any woman you date.
You don't have to both be the same. You can be in a relationship where she is herself (poly) and you are yourself (mono).
That doesn't solve the jealousy issues, but it's not something I have any idea how to help you with, sadly. Hopefully other members will do a better job of it.