if it's only been 3 weeks (I know, I know, it seems like an eternity, I feel for you!), then the fact that you've tried so many things means you might not actually be giving anything a chance to show you whether or not it will work. Often earlier waking means your kid needs more sleep, not less.
If you cut his nap back before the early waking started, then that might be your culprit and you should go back to letting him sleep for 3.5 hours at nap as long as he's still sleeping 11 hours at night. If you cut back his nap in an effort to get him to sleep later, so the change was after he'd already started waking earlier, then the first line of defense is to put him down earlier. Try 15 min earlier but then stick to that for about 3 days, then 15 min earlier than that, so he's going to bed at 7, and then do that consistently for a week (while keeping everything else the same), and see if it helps.
I would also at the same time not get him up before 6:30 even if he wakes earlier. If he's upset, you can go in, say "It's still nighttime, go back to sleep," and then leave and not go back. If he's screaming and crying then you have to handle that how you see fit (Ferber, ignore it, comfort him, whatever works for you as a parent, however you've sleep-trained him in the past), but if he's just awake but playing quietly or something, then leave well enough alone.
Around this time, we taught our son how to read his digital clock: we showed him how to recognize a 3 and a 7 on his clock, because the earliest he can get out of bed at nap time is 3 and the earliest he can get out of bed in the morning is 7. He's often awake before then, but he knows that nighttime isn't over until the clock says 7 and naptime isn't over until the clock says 3. You may want to start talking about this with your son. It takes some of the pressure off of you: it's not your fault that he has to stay in bed, it's just that nighttime isn't over yet, so everyone has to stay in bed. It's the clock that dictates when he gets up, not you. You have it a little harder b/c you're going for 6:30, which means more numbers, but maybe you could just focus on the 6 part, and see if that helps you too.
HTH!