Hi, I have been experiencing the same problems exactly with my ds since starting the transition - it is a constant juggling act. Since keeping a sleep log, I concluded that the tiredness builds up over a period of time, so to combat the night wakings I tried whatever I could to get him topped up for a few days. I let him have an early sleep in the morning for an hour, and pushed him around to get a pm nap in, and then an early bedtime, as early as he could take. This stopped the night wakings.
After this we were left with the 5am wake-ups, but theses seemed to be a result of the early am nap. So once I was satisfied he was rested enough, I went cold turkey to one nap - even when he woke very early, putting him to sleep by 12pm and then to bed no later than 5 hours after wake-up. This seemed to stop the very early mornings!
My ds can tolerate a long wake-up in that although he is tired, he will still nap, if he is overtired it is bedtimes that are hideous!
I am still working on this and need to push the nap back a bit - but there seems to be some kind of logic there - based on reading every posting I can find!!!
HTH in some way - if nothing else - you are not alone!
Justine