Chuy could be right but from what I remember:
1. Deleting game doesn't delete saves, after deleting game you should still find the saves at (Settings) > [Application Saved Data Management] > [Saved Data in System Storage]. It does delete DLC+patches though, those you will have to DL again.
2. Yes, you only need one PS+ per system, the account with PS+ needs to be set as primary/main console and it shares the PS+ to other accounts, regardless the region. You don't get other regions PS+ games though, but you can use the features (online gaming, cloud saves I guess).
I haven't tried cloud saves so can't say for sure about that but I'm certain online gaming between regions works, have tried that myself.