You know what you might do is put both nesting boxes outside in the run area underneath one end of the a-frame...that will give them more room. I see that you are in Florida so cold is really not going to be a problem. I would, however, place your nesting boxes up on some cinder blocks so they don't get 'damp'. An even better idea, since it appears that you 'move' that tractor around (?) is to permanently attach two nest box setups on the end where that wheel is...that way when you move it, the boxes go with you.Thanks, that is discouraging that you think they are crowded. I don't know what I can do about that.
The ventilation should be good inside this coop, the air comes in from underneath and their is roof ventilation, so even in our super hot Florida simmers it seems to stay cool enough at night. Maybe I am making a mistake putting the oven liners over the mesh floor?
The roost bar is a 2x4 with the 2" side up, which I thought was common for warm climates. Perhaps I could add a 2x4 the other way on top of the one that is there.
The second nest was added recently, should I take it out to allow more space? I have a nest box outside, and only one chicken is laying now anyway.
As for the 2 x 4 YES do attach a second 2 x 4 laying flat on top of the existing one, if you can't remove the one that's there now. In fact, make your new roost bar the full length of the coop now that the nesting boxes are moved...that will give the girls more room on the bar for sure!
I wish you all the very best, and update us as you progress with your changes!