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First issue is that if was never opened, then you should probably get it removed regardless of FICO impacts, as their are legal issues as to whether you even have an enforceable account agreement.
Second issue as to only the FICO impact, there are more scoring categories involved than simply AAoA. It may be giving you multiple revolving, helping mix of credit. With zero balance, the CL is helping your overall % util and giving you one account always reporting no balance. How high is the CL? Hard to say the precise overall impact.
As for the account that is still reporting as open, same deal with regard to scoring of util, as a closed account with $0 balance would no longer be included.
Additionally, the CRAs will use the date closed to do their arbitrary account deletion thing at approx ten years from date closed. As the account ages, it wont get zapped at approx ten years if it still has a open status
I would send a direct dispute to the creditor, who is the furnisher of the info.
No need to involve the CRA. They have no independent info bearing on the legitimacy of the actual account, and a dispute thru the CRA might muck up the forwarding of your supporting documentation and arguments to the creditor via use of their e-OSCAR process.