Shouldn't there be more respect for the sacrament of Marriage?

My son has continually dishonored his father and me since he started a relationship with our deacon's daughter. At the time he was living at home he was continually fornicating at the deacon's house. Feeling this was scandalous we asked our deacon to help make sure our son left his house at a decent hour. The deacon became offended. Then everything went downhill from there. We have had to endure a filthy mouth from the girl and threats of not ever seeing our future grandchildren. Our son had told us that she had been diagnosed before with BPD and has attempted suicide before. We had to get our son out of the house because of the friction. Now in the last 5 months he has had nothing to do with us.
Our son has told our extended family that he's engaged to be married now. This craziness has been going on for two years now. We can't give this sham our blessing!

Our deacon told me that he performed his first daughter's wedding knowing that she was already living with her fiance. Our concern is that our son will just go up north where our deacon is from and get married there.

the code of canon law a under Grave Lack of discretion of Judgment (Canon 1095 2*) Did family and friends express serious concerns about this marriage and did you choose to ignore them?

Would the church knowingly approve the marriage of a couple like this? I just don't understand if they would. Shouldn't there be more respect for the sacrament of Marriage?