I'll start with the last one since it's the easiest and go in reverse order. If something is known, eventually someone will use that knowledge, so the best way to prevent it is not to know it.
As for the curse, who knows and who cares? We have perfectly good spells for people who can't conceive. For those couples who can't despite the spells, then maybe it's a sign not to play God. It's sort of like Immortality. Sure you could seek it, but it's probably not what you're meant to do. Also considering the people here, the issue of fertility won't be an issue for decades. Also here's another suggestion, don't mix Muggle stuff with magic ever for any branch. Again, easy solution. It sounds like you guys want to research it because it's 'cool'. Guess what else is cool? Quidditch, but you don't see me running off and joining the Bulgarian National Team.
So we're not a society. I don't see how it's any different from now.
Muggleborns? Are you out of your bloody mind? Bringing them here now is irresponsible and it should be bloody illegal, because you endanger anyone you bring here. They have done fine without us, let them.
New arrivals? You made it clear that new arrivals have it terrible, with no say on how things are done. Guess what? They wouldn't have to worry. They get here, eventually make their way to Hogsmeade and they find papers that we leave.
To the last point: how about Hogsmeade? Or Diagon Alley? Plenty of houses and the owners are dead. Take one you like, take the stuff you need and you're done. Whoever stays behind can get a monthly stipend to buy Muggle products and given time, you can learn to live in the Muggle world.
It's got to be better than being at the whims of the castle and each other, because at this point, I'm not seeing any of the benefits of being together when we can't stand each other and all of the downsides of being forced here. We'll be safer and mentally better away from here.