Found another error:
WEAPONS-ARMOR!R16 - should read =IF(GEAR!B24="chain mail",16,0)
WEAPONS-ARMOR!R17 - should read =IF(GEAR!B24="splint",17,0)
WEAPONS-ARMOR!R18 - should read =IF(GEAR!B24="Plate",18,0)
Values should now be correct, however I think the armor tables need to be tweaked. Most likely fighters will wear plate armor, or one of the heavier armors. At this point a fighter having plate is fairly rare, say about a 5% chance. I think it should be at least 50%, with padded being 5% or less.
I'll look at revising the spreadsheet when I have time.