When I was a teenager, I remember wrestling with the problem you posed here, that if we are supposed to be devoted to God, then how could we ever marry? I think it is a valid point, and Paul certainly talks about how good it is not to marry. I wondered how, if we are part of the Body of Christ, how can we be united to another?
The answer I finally arrived at in my own mind came from the unity Christians have in one another from being the Body of Christ. We're already part of the one Body, part of Christ, and therefore it's not breaking our covenant with Christ to marry and become united with one another. Because we're already united! This, incidentally, provides a reason for saying it's better for a Christian not to marry a non-Christian, because then you are breaking unity of Body.

I agree, marriage, taken as a source of security, is an illusion. But taken in it's best terms, it's a way two souls can draw each other to understand God more deeply, because God is Love, is Relationship, so having that intimate relationship with someone helps you understand what God is.

Fod