For saves:
http://steamcommunity.com/app/35140/discussions/0/540739405840743066/
Might work.
http://steamcommunity.com/app/35140/discussions/0/792924412067258906/#p1 For the retail key. Seems that WB will activate the retail keys from certain regions (the ones where they published the game directly), while Europe and Australia (those two i know about) might require to contact WarnerBros support (contact email on the page 5 of the above link). They might ask for a photo of the box and some purchase data. After that, they will replace the GFWL key with a Steam one (doesn't matter that you have a standard edition, WB will upgrade your game to GOTY edition, as they don't sell the standard one anymore).
Hope it helps and good luck.
Quoting:
"As others said contact 'WBGames.Intsupport@warnerbros.com'. You can find the adress on steam - search for supportadresses for batman arkham assylum.
Explain your problem. In a few days they will you contact you and ask for a picture of your gamebox, booklet with activation key and a proof of purchase. I you can submit the information so that they can verify that you are the owner than they will send you a new key. They will explain what they need in the e-mail."
Alternatley you can use this:
http://support.wbgames.com/