Hi jurijb08, welcome to the forum. I'll see if I can answer your questions.
1. There is a limit as to the number of towns. There are a set number of villages per region (you can see them in each province). As the population of a region grows, the villages become towns in which you can build schools, workshops and the like.
2. Towns have no effect on recruitment. They increase region wealth and let you unlock research. All recruitment is done at a region's capital. Multiple units can be recruited per turn at the regional capital, however, so it's not really a drawback.
3. You cn temporarily occupy towns, which damages them nd reduces region wealth, but you can't capture them without capturing the regional capital itself.
4. Agents appear spontaneously, although having certain building typres increases their chances of spawning. E.g. More schools means more gentlemen.
5. Agents have no impact on your treasury.
6. You can build forts, but not watchtowers.
7. All military units affect public order when they're garrisoned at a regional capital. Some units, such as dragoons, have a policing bonus which makes them more effective in maintaining public order.
Hope that helps!
"Into the face of the young man who sat on the terrace of the Hotel Magnifique at Cannes there had crept a look of furtive shame, the shifty, hangdog look which announces that an Englishman is about to talk French." - P.G. Wodehouse, The Luck of the Bodkins