Complex sentence: He once dated a girl named Tina Jordan, who was a "hard 10" (on a 1 to 10 scale), and that the difference in attractiveness is more than 2 points on that scale, the relationship is unlikely to work out.
Split into simpler sentences: He once dated a girl named Tina Jordan, who was a "hard 10" (on a 1 to 10 scale). If the difference in attractiveness was more than 2 points on that scale, the relationship was unlikely to work out.