11 hours at night is VERY normal at your son's age. We also went through a long period where DD would wake every morning between 5 and 5:30 (ugh). We tried earlier bedtimes, later bedtimes, less day sleep, more day sleep, darker room, etc. We learned a few things - one that DD only needs 10.5-11 hours night sleep and the other that she needs her day sleep. She's very active and when we tried to limit naps it only made things worse.
She's now waking between 6:15-6:45, much better. The only thing that worked for us was shifting the whole routine forward. So when she would wake early we still wouldn't let her nap until 9, or as close to 9 as possible. And we extended A times too. Now she naps around 9:15/9:30 and around 2:30/3. We wake her by 4:30 and bedtime is around 7:45.
If your DS is waking at 5:50 but you'd prefer 6:30/7am, I'd hold off and not allow that first nap until 9:30. Keep the last part of A time low key and quiet so he doesn't get too overtired. Then let him nap from 9:30-11 (if he wants to/will nap that long). If he does nap until 11, second nap shouldn't be until 2:30 - wake him by 4 and make bedtime 7:30 instead of 7. Over the course of a week or so this may help shift his wake time until 6:30 at least.
Good luck!