StopJo, I can't believe your doctor said he was overweight. My DD was 6.8lbs at birth and 7.14lbs at 2 weeks also. Our doctor was very pleased. I really think you should feed him more during the day so he wants to eat less at night. And talk to another doctor. I guess it's just my opinion, but there is no such thing as being an "overweight" infant.
Also, I agree that you should try putting him in one place for all sleeps for now. And what helped my dd was first, swaddling! Big #1. Next was creating a nest in the bassinet. We put a folded blanket that curved at the top of the bassinet, and when we layed her in it, we made sure the top of her head was touching in. Next, we had a sleep positioner, that kept her in place and snug all night. That helped a lot.
And as for the day and night confusion, right now, your son doesn't care what time it is. He's still young, and needs to eat often whether it is day or nighttime. But, eventually, his biological clock will set itself. I agree that you should start a bedtime routine asap. Even if it seems like he doesn't notice now, it is very important to get into a good habit now. And he will probably still wake up in the night for food after his "bedtime" but he will go longer, the bigger he gets.