Vague partial answers..
#1 -- Amazon (PAY videos, not the free streaming with Prime), YouTube, lots of free podcasts (actually useful for video podcasts, though I often download with Tivo, then record realtime onto another recorder so I can watch them faster than realtime in batches)... and some others that I never use.
#2 -- Yes, but you don't get any reduction in lifetime price, unless you do it WITHIN the first month.. I think they give you an 'oops' if you realize in a week you really want lifetime. So I would say go lifetime from day 1.. though if you're really doing the $9.99/month for *years*, maybe it makes more sense to do that.
#3 -- I don't know, but I think G is actually far faster than you'll actually need.. Probably an issue if you have multiple devices trying to use wireless at the same time though.