Here is a useful link:
http://www.babycenter.com/0_how-much-sleep-does-your-chil...
I think, that you need to go according to the child, not a clock.
There is no perfect "formula" for having a child sleep according to how we as adults want.
There is a whole marketing of books, for sleep solutions.
Your son seems to sleep REAL well. Believe me. The only so called "problem" is that he wakes early.
For me and based on the 2 kids I have and how they were when babies... both my kids at that age were STILL taking 2 naps. Morning and afternoon. Not because I 'made' them, but because they intrinsically NEEDED it. Then, they went to bed BY 8:00 at the very latest. Then they both woke the next morning, on average, between 6:30-7:00am.
This was according to THEIR own rhythm... and I observed them and gauged them according to their needs and having a "routine" for naps and sleep daily.
I am not familiar with that book. But "choosing" what time to make a baby or child wake up, does not make sense to me.... unless they are school-aged and therefore have to wake up early for school. Sorry. AND, each child is different. So... there is no boiler-plate template that will fit all babies or kids.
Again, your baby is sleeping REAL well. Sometimes, if we mess with them too much and alter their own natural rhythm... we can make it worse.
Have you ever known a "morning person" or a "NON-morning person?" Some people just ALWAYS wake up bright and perky and early in the morning. Some don't and sleep in ALL morning and are super grumpy if woken up earlier than they are ready for. Well... same for a baby.
ALL my kids lives... they have ALWAYS woken up at the SAME time-frame... NO matter when they went to bed or no matter what their morning/afternoon nap schedule was, no matter what. SAME for all my friends who has more than 1 kid.
Maybe I am just dense... but I would have left him the way he was... and with 2 naps... and then let him/you gradually transition to other nap times as he gets older naturally. BASED on his needs and developmental rhythms. Not ALL kids, "have to" have only 1 nap at this age. My kids, "needed" 2 naps a day at that age up until at least 2-2.5 years old. I knew when they were tired and did not force it. Then when they wake, they wake.
Or maybe, this book method is better and I just don't get it... being dense.
Anytime my kids woke early, especially at growth-spurt periods, I would let them hang-out in their crib until they "called" for me. If they were awake, they were awake. BUT, my kids would often just play in their cribs by themselves and just hang out. So, that is fine too.
But also, at each developmental change and age-set... sleep patterns changes or goes through phases. So, even if a certain method works... it might not be the same all the time... because a child is always changing and their developmental patterns are too.
I am sure, that if I asked my Mom what time I went to bed and woke up in the morning as a baby.... it is NOT the same as I am now.
all the best,
Susan