Yes to all of this except
- Defend yourself against an attacker. You don’t want to bring a knife to a gunfight, especially a pocketknife, but if it’s all you got, it’s all you got.
You also don't want to bring a knife to a knife fight. There's an old line, "The winner of a knife fight wakes up in the emergency room." If you really have no other choice, then having a knife is better than not having one, but the best way to survive a fight like this is to run the fuck away.