And in your example, write out "hospital" in full. See BB R. 10.2.1(c).
You mean "579 N.E.2d 873, ___ (Ill. 1991)."
Incorrect. You need a period after Ill, and no comma after Ill.
Depends on the purpose of the document, generally this is good advice, but it really depends. I've had to put documents into state courts that specified state citations. However, given the OP's apparent level of knowledge, this is probably for some 1L assignment, so yes, the regional reporter is appropriate probably.
Also, Cisarik, 570 N.E.2d at ___. would work. There isn't one correct way to do a short cite, and typically including the case name is a better alternative. Rule 10.9(a)(i).