Sounds a bit like you're not really taking it seriously, to be completely honest. Work on breathing (which is the only way you'll be able to sustain those notes you were cutting short), as well as extending your vocal range. Learn to use your head voice and your mixed voice more often - you seemed to be staying in your chest/speaking voice the entire time, which is very limiting. Also train your ear so you can tell when you're not singing in tune.

Best of luck to you.
Yeah dude.... Until you learn to just let it go and sing balls out, you'll never know what you have. Because of that, I think you have absolutely no range, or power. Let loose and just rip it. You held yourself back so bad it's not even funny.