This is your theme http://themeforest.net/item/black-label-fullscreen-video-image-background/336949?sso?WT.ac=portfolio_item&WT.seg_1=portfolio_item&WT.z_author=eneaa so it use Twitter Bootstrap. The more reason to look at Selectboxit as it supports BS out of the box. Is very easy to modify.
However you have not updated to latest version. Small changes but still, details – focus 
Also tell dev. to update BS, he use old version.
Is from Themeforest but still, it should support child theme. Is popular so most likely no problem. Then you make own mini-theme, a child of parent!, and can modify safely. Can add custom PHP, JS, CSS to files in child theme. Check theme dev. about this – or the 1000s of comments. If you modify core files like header.php (and I think that is what you did) they vanish during next update.
Aaaaarg, http://support.eneaa.com/forums/topic/cant-create-a-child-theme/ so in 2011 he did not suport child theme. Not in 2013 either? Should have known… Well check it out as it make your modification efforts way better. Or get a real theme 