I’m no expert even though I pontificate here regularly. (I read a lot!) I’d say it depends on the height of your run, and the presence of climbing predators. Like raccoons, which are everywhere. But someone else should chime in here.
Yes! What Penny said. It's called a hardware cloth apron and the run should have one all the way around. And depending on any cracks or small openings on the playhouse, it might need HW cloth, too. 1/2 inch is the biggest opening you should have. Sigh. My DH is complaining about how cut up...
Definitely more ventilation! The standard is 1 sq. ft. per bird, so you really want more.
I'm jealous! I wanted something like this to make the building process easier. But DH has built me a coop now, just big enough for my four. (He has somehow caught on to chicken math and doesn't want...