Since he is still a young puppy I think it is best you don't confine him to a crate while you are gone that long so locking him in a small room is a great idea. He can not hold it that long at this point so I would confine him in the kitchen (or another room with no carpet) using an exercise pen. Keep a crate in there as a bed, but keep the door off. Place some newspaper or potty pads on the ground in one section of the pen and his bed/crate, water, and toys in another section. This way if he has to potty he can go on the puppy pads and isn't forced to go in his bed. I wouldn't leave him free in a room just yet because you would be surprised what they can get themselves into. They will chew walls, carpets, get into cupboards and drawers, etc. Good luck!
It looks like you are doing a great job already. Go outside after each meal. Mine were not crate trained but I did have the crates if they wanted to go inside. Keep up the good work and post more pictures