1.) What happens when you place a district or wonder on a tile that has a strategic resource that has not been revealed yet? i.e. you place a district on a tile in the classical era, and there was going to be coal there later? lose the resource? relocated nearby? have access but lose tile yield?
The strategic resource is connected to your trading network (when you research the relevant tech) and can be traded or used to build units that require that resource. You do not get any tile yields from the resource tile on which the district is located (just as you get no tile yields from any other district tile).
2.) PLEASE tell me there is a way to control which city states spawn on a map. Some of them have game-changing effects, others are so mundane in comparison and either way, having multiple trade CS's is one of the most powerful foundations for a great economy. If not, is this something that a modder could do? am I alone in wanting to be able to do this?
There is no game set-up option or other in-game way to control that, but perhaps modders can provide a solution. You might check in the Civ 6 - Creation & Customization forum.