So he will be Muslim before they get married and will follow all the rules of Islam.
He has been brought up Christian but if he accepts Islam, converts to Islam and there is no relation between the two before marriage - is this allowed?
So when the marriage is taking place, the man is Muslim. Then no reason why they couldn't get married. Certainly Yes.
absolutely yes, when someone wants to marry a Christian woman and a Muslim convert to Islam and follow the teachings of Islam, it was very good and maybe it's the way that is given to a Christian god the beaten path through the marriage of a Muslim woman
As long as he accepts Islam for itself and not for the purpose of marriage everything is absolutely fine!
Which means he is "really" Muslim when they marry - no reason why they couldn't marry.