"Not sleeping deeply" isn't a bad habit, for child or adult, in that it is not willfully chosen or preferred over deep, sweet sleep. So thinking of it as a habit probably won't help solve the problem.
Babies wake up because something wakes them, whether a discomfort, hunger, a dream or sense of anxiety, or too much stimulation, which can occur when they are learning new skills or have had too long a day. Unfortunately, some babies are overstimulated by lack of sleep. And some babies just sleep very poorly for their first year. Or two. My grandson was a terrible sleeper until he was around 2.5, and I would occasionally spend an overnight to give his parents a break. There was just no possible way for him to sleep through a night.
Wouldn't it be great if babies could tell us what the problem is? Oatmeal has a fair amount of fiber, and may be too harsh for your little guy's digestion, especially since he's only started it. Rice is usually a better first choice. Some research suggests growing pains can start during the first year, and ear, sinus pain and headache can all sneak in, too. Too hot? Too cold? Something poking or tight? And of course, teething is a biggie, and can be a real sleep-wrecker, especially for the earliest teeth.
I feel for you. It's incredibly hard to keep going and maintain focus, or even emotional equilibrium, when your sleep is disrupted night after night. Unfortunately, that's what lots of moms have to do. Take naps during the day if you possibly can, accept help whenever offered, take care of yourself, and hang in there. It feels like an eternity now, but someday you'll be surprised at how quickly his first years passed.