So, I got a response regarding weight of the sheet. It's exactly 76LB. The thickness is 3.45mm (and tolerance is from 0 to .2mm) - 0.135" (0 to 0.007) so that is what makes up the discrepancy in weight.
I am very close to ordering one sheet but it would be nice if a few people would join me in a group buy. The cost of steel comes to $6.40/lb plus flat rate shipping, which I think is not bad at all.
If interested, please contact me. I will also explore a possibility to have this sheet cut in 3 pieces or so and shipped directly, though I was told I has to be moved to a different warehouse that has shears, and that will have to be added to cost. This would work best for me, as I don't have to do any cutting and shipping.