1/2.) I understand that X-Plane 11 is bringing some sort of enhanced multi-monitor capabilities compared to X-Plane 10. I do not have a multi-monitor setup, so I can't really help you with that, but I understand that multi-monitor support is of a greater priority than it was perhaps in previous versions (or simply XP11 is more capable).
*Bear in mind, though, that increasing the FOV to something like 180° or even 210° will affect performance, as you are telling the computer to draw much more scenery and textures in the same amount of time (compared to an FOV like 60° to 70°, or even 80°).
3.) I am not sure about this "crosswind" effect. I know that FSX handled it much worse in my experience (as in you could barely control the plane), whereas X-Plane handles it better. Albeit I understand what you are saying; I am not sure if this 'fix' is on the immediate agenda for Laminar Research.
4.) X-Plane 11 is bringing multi-core support; the game engine/physics are loaded on Core 0 (to my understanding), then it will load aircraft textures and scenery textures on the next cores. This should distribute the load more fairly.
5.) I don't normally fly with rain, so I haven't really experienced this. However, in the times I have, I don't recalling having this problem. If you consider this one an issue or problem, report it as a bug by clicking here. Please be sure to be specific with the context (describe the location you were at, the specific weather conditions, the aircraft you were flying, whether you are using plugins/addons, etc.). I also highly encourage you to include the log.txt file in the main X-Plane folder. Do not expect a response from the Bug reporter; it is not a support system, it merely helps the developers to diagnose issues efficiently.
I hope I answered some of your questions!