Happy to help with any questions as much as I can.
I'm pretty sure it's 5 square foot per bird, but it's a good idea to give them max space you can. I have mine in a coop I built out of my old garden bed, they seem pretty happy in there.
I would try and find a reputable breeder to get them from. You definitely don't want to breed siblings. You also want to find a breeder who breeds pure birds. There are many breeders who have golden and lady amherst pheasant hybrids that they sell as goldens. I don't particularly like the idea of hybridization in pheasants as it is not really helpful to either species. You either produce sterile birds that are essentially useless, or you produce breeding hybrids that just mess up pure bloodlines of these precious birds. Not to mention in my opinion, pheasants are beautiful enough, you don't need to make them prettier by crossing
This is just my opinion of hybridization. I'm not trying to be provocative to anyone who does breed hybrids. I'm just sharing my thoughts
Hope I've been able to answer your questions well enough.