You can not be sued for asking for validation (though i guess it could be a little like poking a bear with a stick). It is your right under federal law. Asset Acceptance can only report once (though they may continue to update that report over time). You need to dispute with the Credit Reporting Agency (CRA) and have two of their reports removed. Otherwise it is a violation of the Fair Credit Reporting Act (FCRA). IF they refuse to delete the additional reports, then you should file complaints with the FTC, Your State Attorney General.
If you are certain these debts are all out side the statute of Limitations (SOL) then asset cannot sue you over them. However I am concerned, you state the last date of Action is 01/00. Most sates Statutory period is 7 years (coinciding with when negative reports must be dropped). Under the law negative reports can only remain on your report for 7 years, however they may be removed by the person or business that reported them at any time.
Now, ( assume it is also of the SOL), you may be in a better position than you think. From your post you sound as though you want to pay this debt, but are afraid of other consequences. You maybe in a position to strike a deal. You may want to offer a settlement (even if full value), make as a condition of that settlement within 30 days they must remove all negative credit reporting.
Get this agreement in witting so if they do not remove the reports, you can then dispute them and heave them legally removed based on their stated agreement in the letter.
An acceptable alternative may be to have the debt updated to show "Paid" or "Paid In Full" (though less desirable , as they will still show as a collection Item for the next Seven years). But it is better a paid collection than a open collection.
Additionally DO NOT PAY with check by phone, credit/Debit card, Western Union or Money gram. These people have been known in the past to continue taking money out of peoples account with out authorization.
Send the payment in the form of Check or Money Order (cashiers check, etc) by Mail (Certified Mail Return Receipt Requested, or CMRR) or Over night only . The signature receipt or way bill and delivery report from the overnight carrier (fed Ex, UPS, and DHL all have this available on line) along with the cashed check or money order stub will be your proof of payment (in case they refuse to send you a receipt). Since this is a large amount you may want to consult an attorney to deal with them to make sure you are covered.
You are dealing with one of the worst collectors, but talking to them is the best course of action in this case. They are greedy, and may be willing to arrive at a settlement if they know they will get paid.
Congratulations on achieving a position that you can actually pay this debt in full with out a problem.
I hope you are able to resolve this amicable in a speedy manner. Please update us on the situation.