A lot of his behavior is actually still within normal for his age. And some kids just mature more slowly than others. My son (now 8) was very slow in his emotional development and still is "behind" other kids in managing his emotions. I just have to work with his behavior on a one-day-at-a-time basis (sometimes even hour by hour). What I have found is firm and immediate consequences. Usually it is time out and then sometimes loss of a privelige for the rest of the day. Yes, there is a lot of screaming and crying about it, but just stay calm and firm. (And he has begun to understand that all the screaming does is prolong the time out). We also do the same things for his 6 year old brother and it seems to be working well for both of them.
When he talks back, listen to what is under the words. It is often from frustration that he can't express himself. He may not be deliberately trying to be disrespectful. Help him say what he is trying to say the right way. If he still gets nasty about it, then for us it is "you can go to your room until you can talk to me the right way."
As far as the early waking, some kids are just that way. Mind you, necessarily at 4:30, but some kids are just early risers. My 6yo falls asleep between 8 and 8:30 pm (bedtime is officially 8:30 but he's often asleep by then) and rarely sleeps past 6. He often comes in to our room at that point, but he knows how to fix his own cereal as well. I would suggest slowly pushing back your son's bedtime to 8 pm. Then teach your son how to tell time to the hour (either digital or analog is fine, just show him how to tell what hour it is) and tell him he may not go upstairs/downstairs (or wherever you don't want him) until 7. The consequences should be very firm and logical - rather than no Wii, he has to spend that much time in his room, since he didn't when he was supposed to. Make sure there are some engaging things for him to do when he wakes up, and encourage him to come to you first if he needs to leave his room. My son actually crawls into our bed mostly asleep, and I just walk him back to his (like sleepwalking - this could even be part of your son's issue!)
As far as cleaning his room or doing any other chores, most kids his age (and even older) have a very hard time doing chores unspervised. Even something that to us seems super simple, like picking up clothes and toys really quickly, can be overwhelming to a 6 year old. Plan on spending the 15 minute with him that it takes to clean up, even though he is doing most of the work and you will just be directing and keping him on track. On a side note, all our kids (including the 6yo) have chores to help the family, mostly unloading the dishwasher, unsupervised (well, reminders to keep going) - but this is only because we've done it together for quite a while first.
Yes, he is testing his boundaries. It's going to happen a LOT more at home where he knows he will be loved no matter what, than at school (where he is still wanting to please the teacher so she will like him). And its very likely that he doesn't fully understand consequences. Your job is to be firm and consistant (the more exceptions there are the harder it will be for him to learn it) and to help him learn to understand. You can even play if-then games: if teddy (climbs the honey tree, etc) then (he will get stung by a bee, etc), just do this when you're not trying to enforce consequences. And, make sure you praise every little effort and step in the right direction. What you focus on will increase!
Be patient. It can take months for you to really appreciate the change, and even then there will be times when you want to pull your hair out, lol. Just keep working at it :)