1) You can play A-bom with High Places, and while there's no reason why you can't play 7 Years of Famine, I believe it's already territory class so you wouldn't need to. However you still need a character of matching brigade to play them. High Places basically allows you to play some cards as if they were territory class.
2) It would end up in their opponents because A-bom says "place in opponent's territory"
3) "Lost Soul Site" simply means "Site" so you would be able to take Dragon Raid or any other multicolored site.
3.1) Yes you can put Lost Souls in multicolored sites, in general it is meaningless to do so (or even detrimental since you can't use the site for access if its occupied) but sometimes you don't need access and your Lost Soul says something like "When placed in a site..." and you want to trigger that effect it can be in your best interest to do it.