> how do I get him back to his outgoing friendly personality
Are you sure this isn't freindly & outgoing behaviour?
This sort of thing can be friednly, I've met a couple of young dogs that act like this, it's thier way to try to get Buster to play. However, I've also met dogs that act like this that are NOT being friendly in the slightest.
It's really hard to tell, without seeing, what his intentions are.
How do the other dogs react? It
may help to know this, but then it all depends on the temperment of the other dogs. Again using Buster as an example, he will play-bow at a friendly dog, but he will also play-bow at a dog that isn't being friednly, in the first case, it's his way of saying 'lets play', in the second case it's his way of trying to calm the other dog down. There are subtle differences between the types of play-bow, that really need to be seen to explained properly. (same with barking & circling behaviour, it can be playfull or not playfull, there will be subtle differences, afterall, canine play is made up of hunting/fighting/life-skill moves)
IF your dog is being freidnly, it can still get a negative reaction from a dog that is not well socialised, a nervous dog, an agressive dog or a dog that will not put up with a youngsters OTT bad manners, so you can't always judge on the other dogs reaction.
Whatever his intentions, do keep him on-lead around other dogs while greeting to prevent this forming a habbit for now, even if he's just trying to intstigate a game he could get him self in trouble with a grumpy/low tollerance dog.
As for dominance, I don't know about that, but as a dog enters maturity it can start to try to figure out the new boundries and see what it can 'get away with', a bit like a teenager testing the limits of others.