None of this will be dealt with on the phone. Refunds can't readily be calculated by phone agents.
Simply submit a webform complaint to AA noting that your onward segment was cancelled after arrival at ORD and that you therefore wish the entire ticket cancelled and refunded, including the UG fee.
AA should refund the portion paid in cash (including UG) to your CC and the portion paid by voucher to a new voucher. It may also issue some miles for your inconvenience.
I would leave out all of the other back-and-forth as it is extremely confusing and will make it hard for an agent to figure out what you really want.