@number one: I think there was a time, where we made multi-language websites and where we directed the user (like you via 302) to his language. It is not the best way, which language speaks that google bot?
I would say here you can find some answers: http://moz.com/learn/seo/international-seo
@3: I would say social shares and likes (no matter what social network) doesn't has an impact in google ranking. Ok google plus can be seen in SERPs when you are locked in ... but thats all.
Of course websites with a lot af social activity often rank well, but thats correlation not causation. I mean, your social follower may build links, blog about you, share to friends, a.s.o. - that could help, it would invrease your traffic, but to have a Like alone, doesn't help you rank better. Thats my opinion and think I am not alone, even Google told us something like that last days... May be popularity should play a role in some cases, but i really don't want to see popular sites, I like sites in SERPs answering my question in a brilliant way. SearchEngines couldn't see it in a really different way.
@2 sorry -I don't know a good companie for you