1. I think the game has events like that randomly happen.
2. Peds will be scared of you if their aggressive stat is low and you insult them, and maybe other stats play a role too, experiment. You can also force it if you'd like by using the PedSetEmotionTowardsPed function. I'll list emotions at the bottom.
3. Idfk figure it out yourself you lazy fucking twat oml.
4. The game has some sort of spawn point system I've never messed with before. You could change the factions of some peds if you want a quick fix, then edit faction respect so it is how you want it (PedSetTypeToTypeAttitude(faction,towardsThisFaction,attitude))
5. I've messed with the school gates before but not a lot, so I don't really remember.
PedSetEmotionTowardsPed(ped,towardsThisPed,emotion)
0 Aggressive
1 Annoyed
2 Unfriendly
3 Dismissive
4 Very Scared
5 Scared
6 Intimidated
7 Friendly
8 Very Friendly