I don't know if I can answer all of your questions, but I'll take a try at couple of them...

I would not feed wild prey. Wild caught rodents could be full of parasites, harmful bacteria, and other infectious agents, such as pesticides or any other chemicals in their environment. While a snake in the wild could of course feed on them, a captive bred and raised snake would not have the immunity needed to handle such infections, and could potentially contract a lethal disease. This is also the reason that snakes in the wild have shorter lifespans than their captive counterparts.

How likely is this to happen? I'm not sure that I can quantify it into odds, but it's definitely a risk to be avoided.

As far as variety goes, most rodents are the same. The one difference I do know of is that rat pups have a higher fat content versus mice. So if you're looking to put on weight, you could feed those.

I had a green tree python that I would feed chicks when they were in season. He would eat them like crazy. But GTP's are arboreal snakes, that are used to eating birds as part of their diet. I don't know if a ball would go for them. Never tried. But yes, they were sufficient to keep him happy and healthy.

Now, I did have a ball python at one point that ate fish. Once a month I would put a couple of large feeders in his water dish, and he would snap them right up. My vet said this was good for them, because of the Omegas and fatty acids present in fish. Also, pretty amusing to watch. lol.

Hope that helps.