Nice setup. What are you using for water though?

Look like most your questions were answered before my post, but wanted to throw my 2 cents in:

2: Personally, I wouldn't be comfortable with that gap, but I don't think you'll have a problem. I have seen rats do amazing things to get out and usually it isn't that it wasn't amazing, but rather that it was something that could have been prevented but wasn't. Also If a rat can get a good enough angle, they can chew on the bins.

3: I agree about the "when they are weaners" comment, but just in case for small ones I always have a secondary food source in the bin. I use a log, called Nut Munch, that is corn, nut, and what not processed into a hard, dense log. It gives both something to chew since it is so hard, and a food source until they can reach the food. I think you can get similar products , if not it exactly, at pet stores, but since I avoid major pet stores I don't know. Adults will chew it up in no time, but it is great for ensuring the weanlings have food until they are big enough, but won't get eaten up in half a second like normal formal.

4: I don't see why that would be a problem.

5: looks like she is just about there.