medical bills!

This is my husbands issue that I'm working. He had a neck injury and went to a medical center and was billed by 3 separate offices(xray/labs/mri).He had private insurance at the time(2000). I found the insurance provider on line and contacted them and they are sending me all the claims filed during that time period. From speaking with them, my husband probably does owe the money. He thought insurance was to pay the balances after he paid whatever the office asked him to pay at the time of the visit. My assumption is those balances are due to not meeting deductibles(of 2K) plus the difference in the discounted rates paid to the medical provider. This is not how regular insurance works in regards to whats left after insurance pays. Mine always says the difference is over than what they can charge and I'm not responsible for payment. So at this point I'm just waiting on those documents. I tried contacting the original creditors and they all have new billing agencies so no luck working with them anymore as they won't deal with me anyway since it was handed over to the credit agency. We are trying to refinance our mortgage and this is the only blemish on his credit report. So I sent disputes to the credit agencies, and filed with the credit bureau. My mortgage company says all I need the credit report to say is in "dispute" or "paid". I'm thinking that SOL applies here but the credit report and the delinquent dates do not match. If I can't get info from the original creditor then how can the credit agency validate at this point anyway?

So how does the credit bureau count SOL..is it from the time collection agency reports to the credit bureau or from the actual date of service from the original creditor?

Then if we pay the credit agencies then how does that affect my credit score? and does that mean it stays on for another 7 years.

If we don't pay and it drops off due to SOL, then can the credit agency sell the account to a new one and then we start all over again.

Also, my dear husband lived in CA at the time and now resides in TX.