If the statute of limitations has not run, you're not going to get anywhere with an argument that they did not diligently prosecute their case. Their lack of diligence can (and likely did) result in dismissal, but they are free to try to reopen the matter or to refile as long as the statute of limitations has not run. I suspect that they petitioned to reopen the old case rather than incurring a new filing fee. (Motion fees are a lot lower than filing fees.) However, depending on the facts, it is possible that they are reopening the case to try to avoid having to file a new case that would be time-barred, in which case you may be able to build an argument for dismissal based upon the passage of time between default and their petition to reopen -- but that's something we can't analyze without more information.

You won't get the matter dismissed on the venue issue (the claim that they should have filed in a different county, where you reside) -- you might be able to get venue changed, depending on the full facts -- although an order for change of venue will require payment of a transfer fee in the proper venue.
Quote Quoting Florida Statutes, Sec. 47.091. Change of venue; power to grant.
All courts have power and it is their duty to grant changes of venue as hereinafter provided. The order of transfer shall require the movant or, if the action was initially filed in the improper venue, the initially filing party to pay the filing fee required to file a new action in the court to which the action is moved. The payment of such filing fee shall be considered a transfer fee.
You have not shared any facts with us that would help us determine if the four or five year statute of limitations would apply. You should also check your contract underlying the debt, because some contracts include language that requires the application of an out-of-state limitations period that can cause a debt to be time-barred even before it would be time-barred in Florida.

If you want to resolve the case with the assurance that it won't appear on your credit report, you should consider contacting the creditor to see what sort of settlement they might request to agree to a dismissal of their claim with prejudice.