Well 6 weeks is really far too young to be separated from mom and siblings, so you have your hands full. At that age, I would only allow a certain amount of freedom UNDER SUPERVISION. When you are not there, you have to confine the kitten till he/she is probably 3-4 months old. But even at that age, its best to put in the room if you are not there to keep an eye on things. There is too much for them to get in trouble with or hurt - whether its from adult cats or just roaming around.
For the kitten's safety keep him confined when not supervising.
I bred rexes and the kittens were never allowed to run thru the house till they were probably 8-10 weeks old and only then under supervision. When we left the house, the kittens and mom were sent back to their room to stay. By the time they left at 4 months they were fine to run without constant supervision. Still if we were not in the house, the kittens got put in one room.
We got Charlie at 4 months old - and he was not allowed to roam free for another month after we got him. When not at home, he was confined to the library room till we got home.