Reveleation says those who keep the commandments of God and have not defiled themselves with women..virgins. Remember Jesus was a virgin.
Why would God want 144,000 and only men? Christians are not required to keep chaste in such a strict way. We are free to marry in the Lord. Why are these people set apart? They are the remnant.
Christians have two commandments, wheras israelites have like 500 odd.
These Jews will be servants of Jesus Christ...so Jewish and Christian. They will be for the the saving of all of Israel during the Tribulation era, which is actually going to be just like it was for Israel before the Messiah came---Law.