No, there’s no requirement that you use an attorney.
It depends. The “American Rule” means that each party pays their own attorney's fees unless the contract (or statute) says otherwise. If there’s a provision in the contract for attorney's fees, and the court approves the fees, then the answer is yes. If there’s no provision, the answer is no.
Yes, and pursuant to Illinois Supreme Court Rule 282(b), this requirement applies even to small claim lawsuits.