do you think he will change? maybe it's worth seeing a couples counselor to sort it out, but i'd try to find one that is not predjudiced against polyamory.
it must be frustrating for you. you are trying to set up guidlines that you can both agree on....if you think he'll come around, it's worth continuing. if not, i would try to remain seperate for awhile so that you can both think things through, before getting married.
what is it that you love about him? u don't have to answer, but really think about it. also, what are the deal breakers in a relationship for you? are you willing to give up a poly lifestyle? is he willing to be mono?
i hope that you both can be happy with whatever you decide.