Is your dog outside 24/7?
You might not think there are raccoons around, but I wouldn't put money on it.
Adding chickens can bring them, and other predators, to your attention rather rudely.
Having exterior nests will free up some floor space inside.
Chicken wire is for keeping chickens where you want them, many preds can chew right thru it.
2x4 welded wire is what my run is made out of, but all my coop openings(windows and vents) have 1/2 HC.
I used a single sheet of heavy duty vinyl on coop floor no cracks for a spill to seep thru.
I have a walk-in coop inside a large shed with lots of storage space,
sure was nice feeding and cleaning under cover while it rained outside this morning.
Looked at that TSC coop/run....I'd spend that kind of money on a shed for a coop.