I remember my son going through these phases as well. He is over 2 years now and sleeps 12 hrs at night; goes to bed at 7pmish and wakes up at 7amish. What is important is that your little ones nap time is not too long and not too late in the day. No napping after 4pm anymore and no more than 2hrs. When my son woke up early in the mornings, I would make my getting up dependant on his type of crying, but usually a few minutes later, like 5mins, he would resettle and go back to sleep himself. But it sounds like your little one got in a habit of waking up at 5am already and it takes a while for him to adapt to a new pattern again. Also he got used to you rocking him back to sleep, so he can't resettle himself anymore. If it was me, I would let him cry. Slowly extend the time, start with like a few minutes until you go in and then increase to 5 mins, then increase to 7mins, etc.
Good luck!