Can you tell what is those 2 codes for ? 1 of it should be the game it self, another is Ultimate Team?

Game download you will have to go to Apps > Games > scroll to right > you should see Fifa15 Ready to download/install > click on that to start downloading.

Problem with redeem codes are that it doesn't really auto download. So what you might try is go to the store and search for the game. The buy button should now says install.

You bought a SG Set? which region is your Gamertag? I have a US Set, I bought UK Fifa14 code from one of the forumers here and it work. (SG Gamertag)

Can you take a pic of the redeem card? (Black out the code)

Have you tried redeeming both codes?

You do not need to own a game first before purchasing any add-ons. To me it's likely some kind of purchase issue. I'd suggest you go and contact support and ask them about this problem.

Yes, all my games (and apps) are inside my external. It's only 1TB. There's no gameplay impairement whatsoever since the requirement for storing games on external is that the drive must be a USB 3.0. However, if you restore your console to factory setting, initial launch of a game/app will take some time as the OS need to initialize it. Then it will launch as usual.

it is normal to be hot it is after all a gaming PC fit in an Xbox, The GPU & CPU is producing most of the heat. Place your Xbox at a place with good air flow, I cover them with cloth or whatever I can find when i'm not using it to stop dust dropping in the vents >.>