yes if it is hungry but no if not
mainly insects wild grain
Everything
Yes they can, so can you.
of course yes, because wild rats are bigger than chicks but it does not mean that if you are bigger than other animals you can eat them absolutely
Your dog will be fine. Dogs are decedents of wolfs they can eat raw meat and digest it properly. I would be concerned if your dog does not have it's rabies shot up to date and was bitten by the rat, or if your dog just found the dead rat the rat may have been poisoned. If they are acting normal I wouldn't worry about it. You can also go to the vet althought your dog is probably fine!
they can get a disease from the rat if they eat it
Rats will eat anything
Rat..or cow...or cat..or hog...YEAH!!
Of course; the poison is still in the rat and your dog will ingest this. Since your dog is larger than a rat it won't affect it as much, but lots of dogs will die or get very sick if they eat rat poison by themselves so immediately call your vet. Never let your dog eat dead animals that they haven't killed themselves (don't let them eat if they shouldn't have killed as well as it will encourage them to kill more) and don't let them eat animals that are being poisoned in your area, eg: rats, mice, rabbits, etc.
A wild rat can attack and kill a rabbit if it is hungry enough or feels threatened. A rat does not normally attack animals larger than itself unprovoked.
No
Usually, no. But in extreme situations when the rat doesn't have anything to eat and it's on the point of starvation then it might eat another rat.