Aw! you are most welcome.
I believe the consensus here would be that they don't need heat at 7 weeks. You also run the risk of coop fires with a bulb. If they are feathered out they should be fine. Ventilation helps...it is the humidity that creates all the problems. They now have down coats covered with feathers.
I would put them on the roosts.
Dustbath: you can get creative with it depending on room. Some people do a fun barbecue fire pit kind of set up dug into the ground. Easiest to start with would be a plastic tote/tub. Or you can fill up a kid's swimming pool...pretty full tho. Some combo of the below ingredients, making sure the combo is quite loose... starting with the dry dirt (if you don't have any, lol top soil bags would be fine). I would have it in the run and in a sunny spot....they LOVE the sun with the bath.
What goes in? Dry dirt, and then you can mix in some peat moss if you like, some folks add sand too, no problem, but the best addition is some wood ash, helps prevent lice and mites. It will fly everywhere, ergo the pit or a box with high sides.
And lets see some pics of your creations!