I can tell that FIFA 12 is compatible with Windows 7 x64 (had it until a couple of weeks ago, now I'm using 8.1 and FIFA 12 still runs quite flawlessly).
There are a lot of editing programs such as Creation Master (CM) and DB Master and they all work under Windows 7 x64 (they also work under Windows 8.1). The only CM12 bugs that I can remember are these:
- It never sets the correct "shortsstyle" value in the "players" table when assigning long pants to GKs.
- it hardly ever saves the "jerseynamefonttype" value while modifying the teamkits table.
- Upon importing new textures to a kit, it might happen that the preview 3d model gets messed up (logos andd numbers misplaced). Unfortunately, the only suggestion I can give you is to save the rx3 you're working on, close and reopen CM12 and everything will be fine again.
All in all, these are things that you can easily override by using DB master or by testing kits ingame (or restarting CM12 upon the insertion of a new texture).
Other than that, I can advice you to look for the 12/13 FIFAmania patch for FIFA 12 which has all the stuff from the 12/13 season, I don't really know about World Cup patches or such.