Are you sure about that? They were only sponsoring/advertising on Bitcointalk IIRC (I'm not entirely sure though).
Not sure if this information is correct but this website says amazon.com.
Yes, the information is valid. There are plenty of websites that offer whois tools (some with history, but that's usually a premium feature). You could, optionally, run something like 'tracert bitcointalk.org' via command prompt and you will notice the AWS IPs.