Carl, I do not know if one could possibly argue a refutable claim using the bible to how to define marriage.
Like you stated: We know that Jesus attended the wedding a Canna but we don't know if the participants were already cohabiting.
You know there was a person, at work who lived with her boyfriend at the time, which they are now separated.
However at the time, I explained to her even though you both are not married by papers, you both are married because you are together with each other because of you have both made the decision to try and stick it out.
She denied that fact, and however that is the way I see it for anyone who is living together with someone they are either trying to work it out with and make life work together between each other.
Man and woman come together after leaving, their mother and father, and living into a new life with someone they desire to be with, and if they agree on these matters, by definition they would become one flesh, (living together, living to support each other, children, having to pay bills together, Ie: becoming one in togetherness.)
(Like Yeshua, stating that Him and His Father are one.)
I rather marriage be this than have some pastor or someone who thinks that they are ordained to grant me the right by the Power of God, and by the state. it is pretty much just worldy, even though I will say if you wanna just go up the justice of the peace and get married together by last name that is fine to but it's all on how you really look at it I believe.
Just some thoughts. Thanks for reading.