You said he likes another girl, and that girl doesn't like him. You still have a chance. Don't always think that girl's personality is what he likes, but give full play to your advantages.
Your first question is probably the most difficult to answer, because it is difficult for me to understand him only from your statement.
In fact, it is difficult for a person to judge by arrogance or inferiority. These are just two aspects of him. He has no real problems.
His external image is cold and aloof, but it will also make him very lonely, so he will confide in you that night. This is the expression that boys in single-parent families are eager to understand on the one hand and afraid of being hurt on the other.
If you just like his aloofness, you'd better give it up. Although he has aloof capital, aloof appearance and aloof side in front of many people, he is unlikely to be a completely aloof person unless he was just lying to you that night.
Generally speaking, boys from single-parent families rarely believe in love, but once they have true love, they will cherish it.
In fact, he can show a different side in front of you than in front of others, which shows that he at least regards you as a good friend. In fact, I think it's good that high school can maintain this relationship.
If you are really determined to chase him, you should always care about him and comfort him when he is sad (this may be difficult, and arrogant boys rarely show their emotions), which should be successful.