A chicken saddle is basically a covering that straps onto a hen's back, which can protect her from overmating.
Here are some pictures and info. They're kind of a luxury, but if a hen is being overmated they can really help. And yes, roosters will most certainly mate even if the hens don't sit on and incubate their eggs.
Larger flocks require bigger coops, and more feed, but other than that expenses are pretty similar. And the time commitment is almost identical if you get big enough feeders and waterers to last your flock a few days. I certainly wouldn't go too big at first, but maybe you could get 5 or 6 hens to one rooster? Or you can start with 3, but if overmating becomes an issue you could always add more...if you have enough coop space, that is.
Well, hawks may not be too big an issue as long as you don't get bantams. If they didn't go for your rabbits, you might have little to worry about! It sounds like the hawks near you have lots of other meals to eat.

Chickens aren't the preferred prey of hawks. The best defense is having shelters for your hens to run under for cover when the rooster spots a hawk. Bushes are great, or I've seen people tie branches together into little teepee shelters.
Snakes...hm. Most snakes are too small to go for adult chickens, but chicks may be at risk. Snakes could also eat eggs in nesting boxes. I wouldn't worry too much about snakes, at least once your chicks get bigger...I haven't heard many accounts of snakes attacking adult chickens. Others may have more personal experience with snakes...they're not an issue where I live.
I don't know about the wild waterfowl you mentioned, but I doubt it would be a problem.
No, definitely do NOT clip their wings. I'm glad you questioned that advice. Clipping wings is good if you want to keep chickens contained in a fenced area, so that they can't fly over a four or five foot fence. But there's no reason to clip a free-ranger's wings, and it will severely limit their ability to avoid predators. You're right, they won't wander far from their coop anyway.
Shade in hot summers is super important. It's not that it needs to be everywhere, though, it just has to be accessible. Shade cloth is great for that — you can find it at Home Depot and stores like that. If you have any trees near the chicken yard away from the woods, that's great too. Here's a great post about keeping chickens cool:
http://www.the-chicken-chick.com/2012/04/beat-heat-helping-chickens-survive-high.html
Water and chickens seems to be a contentious topic. Some people have had no problems at all. Others have had chickens drown even in the very edges of a pond, since their mobility drops dramatically if feathers get drenched and heavy. I'd do some research on that. To be safe, you could put some stakes with poultry netting around the pond to dissuade the chickens.
I don't have any experience with those breeds, but maybe others will.
Great question. Most hens don't have the instinct to sit on their eggs and incubate them. It's been bred out of production breeds, since if hens are sitting on eggs, they're not
laying eggs. But some hens do go broody, and what that means is that the hen decides she wants to sit on her eggs and allow them to hatch. More info here:
http://www.mypetchicken.com/backyard-chickens/chicken-help/What-does-the-word-broody-mean-H84.aspx
Hope that helps!