there is a pipe in the top right pocket of the clothes, helps you breath.

use the knife in the pocket open the box with red&green lamps.
just click on the white button at the bottom "airvantage", help you breathe

Actually there are two keys to find (black and blue).
The black key is inside the single crate by the switchboard with all the red and green lights. Use the iron rod to open the crate.

You'll need to turn on what I think are freezer thingys in order to obtain the blue key. To open them, use the swiss army knife to open the board with all the red and green lights. Once opened, notice that a screw on the upper right corner is missing. You need to find that screw and place it back.

It's next to the iron barrel. Use your mini flashlight and click on the right side of the barrel.

For the code:
It's actually different everytime you play the game. I've played the game twice and it has been different numbers. It is a 4 digit code, and as some people have guessed, it's the number from the paper in the bin plus the number found in the paper file.

'highlighted' the card, did you place it on the area where it says 'card'? If not, you need to place the security card onto it. Once you do that, the number screen where you input the code should highlight green. Type the numbers in and press OK