My first baby had a few sleep challenges.
First, I think mine might have slept too much - because later on, I did later bedtimes and my babies all slept more soundly and straight through. So you might want to push back that 7 pm bedtime.
Second, my first born had fluid in his ears - it could last for weeks after the sniffles had long dried up. In the end, he needed tubes. A trip to ENT was all that was needed to assess and fix. Another one of my children needed tubes also. It's more common than you think.
It created pressure when he lay down - so he just didn't get into a deep sleep. May not be related whatsoever, but good to rule out. A regular doctor cannot always tell. Also, helpful if he's had ear infections to keep track of how many.
I didn't breastfeed past about 11 months. By then, they were completely eating and able to take formula/then milk. My oldest had gotten into habit of just waking in the night for a snack, but as others have mentioned you have to cut it out. I would up food at last meal/before bed to see if that helps. But ultimately, you just have to stop providing him with snacks at night. I switched to giving him a sippy cup with water and he lost interest, and slept through.
I had done the 'cry it out' method with this baby earlier. It worked, but not for long. If there is a sleep issue (with mine, it was his ears) it's kind of cruel. I had no idea he had problems so looking back, I feel terrible about it. When it works well (as with my other babies) you let them fuss but go in when you feel you should. It worked well for my others and I wasn't a wreck.
Breast can be comfort too and maybe your son, waking wants comfort (not so much the milk). Does he have a soother? You might not want to introduce that into the mix at this point but he'll have to find another way to soothe if not breast. I had a little bubble light machine in their cribs (attached) by Fisher Price. I'd hear that go off once or twice a night in the beginning and would do the trick. It was just enough to send them back to sleep.
Best to you. It won't last forever. I would try the bedtime a bit later thing first myself, up the food (evening meal) and do a big feed (I did a bottle before bed because my milk supply was at its lowest in the evening after a long day). Good luck :)