Yeah, putting them down earlier doesn't equate getting up later! Unfortunately babies sleep habits constantly change. I know the early mornings suck.
Maybe my story will make you feel better :o) My daughter is a year old and she started sleeping from 10pm-5am straight around 2wks and then around 3mo changed to 2 wakings between 10pm and 6am, then around 4mo changed to 2-3 wakings and that lasted until about 10mo. After 10mo of sleep deprivation, I finally forced her to sleep through the night. My hubby slept in another room and I would let her cry when she woke up - it took about 4-5 days. Now, at 1yr, she goes down around 8:30pm and her mornings start anywhere between 5am and 7:30am.
There are a lot of things to take into consideration too - are you breastfeeding, does baby co-sleep, does baby sleep in your room or own room, is baby teething? My daughter was breastfed and co-slept/slept in our room and I'm sure this is why she woke more often. I also noticed when she was teething there was a certain time of the night it seemed to bother her most. Maybe baby is cold/hot? I know in the early morning hours our house is cooler and this has caused some early wakeups and she does go right back to sleep when I get her.
Honestly, I'm OK with the cry it out method but I don't let her cry for more than 5-10 minutes depending on how desperate it sounds. I feel like crying for 30 minutes without you is too long, especially for a 6mo old. If you do want to try to let him cry it out I suggest going in every 3-5 minutes just to pat him on the back and let him know you are there. A baby that young hasn't learned "object permanence" yet - which means if he can't see you, you're not there. How sad and scary this must feel. You may be right about this not being a natural wakeup time but something has him waking up enough to realize you are not there.
Good luck.