Hi Diana,
First of all and before choosing a method we have to adress Anthony's reasons for waking so early. They can be as multiple as being overtired, or teething molars (he's at the exact age) a developmental reason, change in his routines /(you mention you're trying to switch to one nap). My first suggestion would be that if you're in the boat for 1 nap a day, then do it and if he wakes early and needs to nap early in the morning, try to extend his awake time by offering a snack and keeping activity time very low key. Then if he still wakes early from nap, do an early bedtime instead of a second nap, that should help him make up for lost sleep and still keeping the one nap a day structure so you can work on building a schedule that works for you both. This transition is really difficult and slow. Early wakings come in the combo, unfortunately. But if you keep consistant you should be able to see results in a 2 week period, if lo's not ill or teething.
HTH and please post your schedule back to start working with it!