Good job. With a body like that you'll probably have no problem keeping you bodyfat down. I wouldn't get hung up on keeping it ridiculously low as you say since that could curtail you results but keeping it low is probably realistic. I would go ahead and do maintanance plus 500 or so calories and see if you gain and then if you don't bump it up slowly (if you're not already taking in that amount then you may have to build up to it.
Yeah, deadlifts like Sentinel said. Start making squats and deadlifts a priority not a secondary consideration. Looks like arms and chest are not problem for you and those two will affect overall body growth to a greater degree than you can imagine. Make you thicker and more robust looking.