Perisno does have a learning curve and it takes a bit to get used too. With that said every play though is different. You can also play around with the zann invasion date if the default date isn't up to your liking (next play-through). It's very random... but the biggest weakness of the zann is...
Lorewise not really. In-game though, the ruler is a bit stingy in that regard. Best way to get a fief is to start the siege yourself, and ask for the castle or town to be given to you.
Though I think you mean after you joined them as a vassal? Because you won't get fiefs being a mercenary.
Steam updates automatically once you subscribe to the mod.
Also I recently merged the hotfixes into the main download, so just download the main 1.0 file and you are good to go, if you are using a non steam version.