I almost spoke this morning, but sometimes I think my thoughts are too profound for such a large and diverse group.
Your excellent description of marriage inspired the following epiphany about marriage.
Does a marriage truly exist in God's eye's if He is not the unifier of the marriage? My understanding of marriage is we pledge to each other, but we don't pledge to God. Without God being the unifier of the marriage is almost destined to fail.
It's kind of like local TV when we had just TV antennas. It was easy for something to get in the way of the signal. Thus the unification is local, such as just between the man and woman, like we pledge to each other at our marriage.
God might be looked at a little bit like Satellite TV, both the send and the receiver go through Satellite, thus the local object which might normally obstruct the signal are no longer an issue.
My thought of why Jesus, as you interpreted, so many people won't be able to stay married is the same reason so few will get into heaven. If two people shared the same love and faith of God, then how can the marriage fail?
In a book I read, "The reason for God" by Tom Keller, he talks about how we base who we are on anything else other than God is doomed for failure, because God is the only permanent thing in our lives. He implies, we seek marriage to fill the gap, thus putting an unreasonable demand on the spouse to be "God" like and when they are not, well, the marriage fails.