I've found an error in the spreadsheet. It does not give half Strength bonus to off-hand attacks for TWF. The Brb 20 TWF listed gives 4.86 DPS per Strength bonus, but it should only be 4.86 * 1.4 / 1.8 = 3.78, or a difference of 1.08. For a 29 Strength bonus, this is a total of 31.32 DPS higher than it should be.