Taking the international debit card activity out of the equation, I would say you would only need to file on the non-customer who cashed the checks. I say that because writing someone several checks for $9,500 is NOT structuring for BSA purposes as there is no cash involved. It was the payee's choice to cash those checks versus depositing them into his account.
Now, taking your already existing concerns about the business account, I might view it differently. But then, if you filed it on the business, you might want to include the whole big picture in the filing (i.e. file it on the business for suspicious debit card activity PLUS the large checks, and include the non-customer in the narrative as cashing those items). I think reporting the business as a suspect solely based on writing 4 checks to someone (who chose to cash them) is stretching it a bit.
I also share the previous poster's concerns about the account officer not being willing to contact the customer and ask more questions. That would irritate me to no end.