You can't ask public bodies to do research for you. That's the public policy balance in our FOIA laws: you can get almost anything (and: talk to Matt, you really can get a lot of stuff), but you have to be specific about what you're asking for, and it has to be "at hand" for the staff responding to the request.
They send emails to IT. The classic example of a thing you can get through FOIA is large-scale dumps of emails from Exchange Servers, which is also not something a Clerk can do themselves, but which IT staff can immediately retrieve.
Leave the "Clerk" bit of this out and just imagine you're requesting straight from the IT department. What you can do: get anything not otherwise exempt that they know how to retrieve (it usually helps to provide example commands in the requests). What you cannot do: ask them to go look around and see what they have. That's research. Research is your job, not theirs, under Illinois FOIA.
Maybe? If you work there, I guess? Or if you're really nice to them? But they're under no obligation to help you. The tradeoff in Illinois (and most other good FOIA law): you can get almost anything you want --- way more than most people think --- but you can't get public staff to go do research work for you.
Again: this is why pulling schemas is so valuable.
"I want your data"
"What data?"
"What do you have?"
"Ha ha. No. Tell me what you want"
"Your data that is the metadata of your data"
"Well actually..."
...