Nope. This sounds like a bug. They should have roads.
No, there is no list of events. However, the idea is that you pay the 10,000 or whatever the cost to prevent being attacked. The fact that you get some troops is a little bonus. It's also meant to be a gamble too. So knowing which one is worth paying for spoils that .
If you want the unique characters it is very simple, the text of the merc event mentions the name of the character. For the catalan company there is no mention of a character which means the event has no unique character.
There is no such unit as croatian light hussars. You can go look in custom battles where you can see all of the units available in the mod.
The Banner of St George is only recruitable in Stuttgart by any HRE factions.