I'm not sure how the x12 is awarded; does that just mean the SkyMiles you get for the spend itself (ie marketing gibberish), or is it supposed to be on top of the SkyMiles for the spend?

It's true that it's frustrating that Delta's calculator could screw up so badly on a fairly simple calculation. But the estimate was nearly an order of magnitude high, and that was obvious; if you get 11 (or 12) SkyMiles / US dollar spent excluding taxes and fees, getting about 50 Skymiles / CAD dollar spent including taxes and fees (66k/C$1300) should have been a red flag that the calculator was wrong. In fact, you said in your original post that you thought it was too good to be true, an indication that you realized something was wrong with the calculator. Given that, I would have checked the calculation myself and complained to Delta at the time. I would not have taken a calculator that was obviously wrong with a disclaimer saying it may be wrong (and tough luck if it is) as a binding commitment.