Once the Combat/Conquer systems are in place (next update or the one after that, possibly) there will be a lot of content as you train and work your way through the various districts :)
As for your questions:
1. The Ghost Festival, as with the other events and locations, will either have a role to play in the war or else will have been destroyed/vanished. No festival for Kana, for example, as nobody's feeling particularly festive :P
2. Some of them are! Others... not so much.
3. They're probably fine. Isolated... right next to your arch-nemesis' demesne... on a farm... with only Annie and Kana to guard them for the last three months... yeah, they're probably fine!
4. A little bit more, but the Act Two finale was the last timeskip so if you want to know what happens to the Rinkos, Nuli and Luna then you'll have to play the sequels! :)
5. MC starts with a sword (that's what I'm modelling the combat system around right now) and will later be able to find and equip other weapons such as guns, magical staves, and so on.
Hope that answers everything! In an appropriately vague and spoiler-free way, of course ;)