Hi,
I cannot give you a complete answer to your question. Nevertheless, as the data that you will work with is highly sensitive, I would strongly advise against using Excel, which does a great job as a spreadsheet but a very lousy one when security is involved.

There are lots of database programs out there but I suppose you could find one somewhere that is tailored to your kind of needs and can offer strong protection.
If money is a problem search for open software mostly based on Linux.

Don't worry, Linux is not difficult at all ,is virus free ( and free ) and has many advantages over Windows.

Perhaps some more savvy member can help you better than I can.

Good luck with your endeavour

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