Excel spreadsheet into a MySQL database tables
I did not look in detail at the data since I belief you can normalize it yourself, but from what I've grasped out of your posting I would say you are doing everything right.

One warning though: Likely you will encounter a lot of existing inconsistencies in the excel sheets. You must fix those in order to import and normalize the data correctly. This constitutes a high initial effort.

The alternative (keep the data in the form it is) instead will rise the maintenance costs of the application.

In the long run I claim that the additional initial costs will be less than the regular addition in maintenance cost.