Hi Honey,
Is he going through any developmental leaps at the moment, ie learning new skills. I remember that Sam went through this on several occasions. Often when they are 'practicing' something new their little brains can't switch off (as with adults, we've all been there) and it disturbs sleep. If this is the case, it is just a matter of riding the storm. If you haven't noticed anything yet, it may be something to watch out for.
I see his day is pretty long. I wonder if it would be an idea to shorten his day, and see if earlier bed time will help him sleep through
Sometimes it is better to cap the nap, and go for early bed time. It's scary when you're experience early wake ups, but often it could work out. Advise is often to push the nap out when getting EWU, so LO's don't feel like they can just tag sleep on later in the morning. Then the long morning A times over rides the short afternoon, meaning theoretically LO still goes down early. So something like this:
WU 6 am
Nap 12/12.30 cap at 1.5
BT 6 pm.
If no joy with this ^, there are other things you can try. Thoughts
Oh BTW it's fabulous that he is such an independent sleeper, so well done on that. I certainly would keep it that way, and not even try to help him by holding etc.
(HUGS)
x.