Couldn't get my order to go through either. Called up MS support and was told to check with Bank of America if there is a hold on my credit card. Called up up BoA and was told there is no hold. Definitely an issue with the MS site.
Yes, it's legit. I've bought a bunch of MS Points codes from there before. I did get one code that was invalid but their customer support replied in about 30 minutes with a working code.
I've had this game on my wishlist for a while now and this is the lowest I've seen it: http://amzn.com/B006JKARN0 Also comes with a 30 day PS+ trial.
Enjoy!
I emailed customer service again and should be getting a refund in 2-3 business days. This is the second time that I've had an Amazon order lost during shipping.