> "1. Couples who live together before marriage are more likely to divorce"

If you do not correct for age, this data is quite meaningless.

- Older people seldom lived together before marriage.

- Younger people more easily do.

Now, the higher divorcing couples are because of the living together, or because they are younger? (i.e. less mature, more individualistic, more prone to FOMO, etc.)

Also, as MXM already commented, "Correlation is not causation".