My DS2 is 24 months, a little older than your DS, but still has exactly the same routine as he did when he transitioned from 2 to 1 naps at roughly 15 months. He wakes approx 7 a.m., has about 5 to 5.5 hours A time (so up til approx midday) then naps for anywhere from 2 to 2.5 hours. I never let him sleep past 2.30 to preserve bedtime. Bedtime is approx 7 p.m. and he generally falls asleep straight away.
I know every kid is different but looking at your routine (and being aware that you are only
just making the transition from 2 to 1 naps, I would suggest your DS may be overtired. If my little guy woke at 6.30, I would have him in bed no later than midday or else he's guaranteed to sleep a shorter nap...classic OT "symptom".
Based on waking at 6.30 a.m., could you try this routine:
NAP 11.30 - 12 p.m.
WAKE 2 p.m. (hopefully
)
BEDTIME 7 p.m.
So basically 5 hours up, two down, 5 hours up then bed. If his nap is shorter, I would suggest an earlier bedtime. I still do this with my DS to combat OT, but he is getting to the age where a shorter nap or
slightly later bedtime doesn't affect him too much. HTH
ETA that, thinking back, DS required a bit shorter A time during the transition. Bedtime was closer to 6.30 p.m. back then. You should be able to work out if your DS fares better with a longer A time in the morning or afternoon