I will play some multiplayer games at some point now that I have this thread sehorned.
For challenge two I think there are a couple options. I agree with putting your abandon south of africa, but I kind of think the spot in canada just south of south africa would work too. It has the same benefiit of being a single entry point but it also blocks the seven point canada province which is slightly better. Only problem is south america has way too many countries for four points.
I think a kamikaze mission to the netherlands might be best, locking up africa as you go, but it seems like the computer just gets there faster than you no matter what.