You need to find a magazine in order to load more rounds. This one in particular http://dayz.gamepedia.com/15Rnd_FNX45_Magazine

Further info found from other players it seems that if the zombie hits you in the head causes the instant death. Now i'd like to know if that's how it supposed to work or if it's a glitch

Some other people have faced that issue as well http://forums.dayzgame.com/index.php?/topic/182995-slightly-confused/

Or try exiting the room by going backwards, sometimes it works and rolling might work as well.

Well they ain't hackers they just glitch through the wall. As long as they don't use a third party software their not hacking and can't be detected by battleye. They are just glitching inside the wall and shoot at you

Also by hitting T at first time you can go in semi auto mode but hitting the key again to go back to full auto it won't work