Few questions about my new coop...

Ok, I found someone to build me a coop, and it will be here in just a couple of days, but I have a few questions about it that are bothering me, so I thought I would pose them here.
First, my coop will have no floor so we can move it around the yard and let the birds eat the grass. My concern is predators as we have a lot of raccoons, opossums, coyotes and skunks in the area, and I also suspect weasels too, and my neighbor said that before she got her guineas she had a problem with opossums digging in from underneath her coop, and raccoons too, and she lost several birds to that. Personally I don't want guineas cause they scare me, but I want my chickens to be safe nonetheless. So, I had an idea, and please, let me know if it's a smart one or a stupid one: I had the thought a few days ago of, what if I laid chicken wire down and set the coop on top of it? The birds could still graze the grass, the coop could still easily be moved, but digging predators hopefully won't be able to get into the coop. Is that a wise idea?
Second, my coop is sort of like a big metal shed. Here is a picture of the practice coop he built. He's building me a similar one, but a little better. Here it is:


And I am worried about winter. I discussed that with the man building the coop and he said he would make two metal panels to cover the chicken wire in the front to block the cold winter air, but then I have to worry about them not getting enough sunlight. Is there a better method to blocking the cold winter air? Should I somehow run lighting out to the coop and use artificial lighting? Or will letting them out into the run be enough?
Third, when is it too cold to let the chickens out? This last winter we had some super cold weather where it got to 17 below, and we lost a dog to the frigid cold, and I don't want to lose my birds because of it. I intend to get a heater for their water so it doesn't freeze, but I also intend to get at least one heater for the coop too. I looked into a brand called Sweeter Heaters, and I intend to get at least one, if not 2 for the coop. I am trying to reduce or eliminate the risk of frostbite and death in my flock. I care deeply about my birds and I only want the best for them.
Fourth, SHOULD I have a floor in the coop? And if so, should I put down linoleum or something easy to clean like that? I could probably build a platform to set the coop on if I have to. And if I get enough people saying it is a good idea, and I build the floor, what kind of bedding, if any, should I use? Right now in the brooders I am using pine bedding. I worry about the dust affecting them long term though. The consensus here seems to be that hay is the best choice. I want to know if I should use it too.
Fifth, when I put their nesting boxes in the coop, which is the best, metal nesting boxes, plastic, wood? My mom suggested if I go with wood that I should put a sort of shellac on it, to act as a barrier and make the boxes easier to clean, but would that be dangerous for the birds? Metal nest boxes seem like the birds would freeze when they try to sit in them in the winter, and get overheated in the summer. What is the best route to go? And should I use hay in the nest boxes?
And lastly, I also have ducks. Two mallard ducklings approximately the same age as my older chicks (Currently 5 weeks old), and I understand what everyone says about how messy ducks are. I am thinking that putting them in with the chickens is a bad idea, at least to sleep, so my thinking was, I plan to attach a big dog run to the chicken coop, and I was thinking, if I get the chick-n-hutch (sp?) that is advertised on so many websites, and I put it inside the run but not in the coop itself (at least during 3 seasons), and let them out to graze with the chickens during day and put them up in the hutch at night, is that ok? Later I plan to install a small pond, or at the least set up a really BIG pool for them separate from the chickens that they can be brought out to during the day, and then brought back to the hutch at night.
I am sure I will have more questions as time goes on, but these are the ones that are bothering me the most right now. This is my first flock of chickens, my first coop, and my first ducks, and I just want to do everything right. Thanks everyone for any help you can give me in these areas.

(Edited for misspellings. I tend to type too fast!)

 

So far the breeds that I have are: Silver Laced Wyandottes, Amber sexlinks, and for bantams I have: Cochins, Silkies, one OEGB, one Sebright, one Silkie cross, and one Mille Fleur. I do have a spot in the yard where a garage used to be, and the concrete foundation is still there, albeit cracked as it is, it's not that bad. I could set the coop on there. And I should face the coop South? I will definitely invest in something to bring into the coop as an area to protect them from the elements until next year when I can either insulate it myself, or have the guy who built it possibly come back and insulate it. If I do it myself, which most likely I will have to, what is the best method? I do believe that he put chicken wire all the way around, so it's under the metal siding too. Would the foam boards that you buy at say, Lowe's or Menard's work? And then put up some sort of subwall on the inside to block the foam? Windows, I think I can rig windows. I was thinking of that myself and wondering why he didn't put in any windows. I am thinking of cutting a square into each side, screwing chicken wire in place, and then using the piece I cut out as a flap that can be raised and lowered depending on the weather.
I thought we had weasels here. I was pretty sure I had seen one not long after we moved in down by the drainage ditch at the back of our property.
Long term, if I do place the coop on concrete, will the birds be ok in the winter? Cause concrete gets pretty cold. And is there a way to weasel proof the coop? I'm sure I will have more questions as people give advice, but at least I am getting a better idea of how to make my coop safe and chicken friendly (not to mention better for me!), so thank you everyone for your advice.

 

Thank you very much Pat. I am going to check the condition of my cement once the rain finally dies down (It was once a garage floor, but the garage is long since gone) and I will definitely invest in foam board and maybe some plastic beaderboard, or something along those lines for the inside walls. And I was already thinking that chicken wire wouldn't be enough. I'll see what's on the market that is stronger. And I will see what I can get to go inside to keep my chickens safe at night. I suppose I am a worry wort when it comes to my pets. I mean, I don't even let my chihuahuas go out to pee at night unless someone is out there with them because I worry about the coyotes. A neighbor lost their chi to a coyote attack a few years back. If chickens weren't so stinky, and I didn't have so many, I'd be racking my brains to find a way to keep them inside, but I know they are outdoor birds, and I will make the outdoors as safe as I possibly can. Thank you so much for your help.