Assuming you earn 1.5 Qantas point per dollar spent and your after tax deduction % surcharge is correct, your math seems sound.
I never used B2B specifically, but I earn points too for the surcharges from payment services I have used.
1.1cpp is a reasonable acquiring cost (not excessively high). As long as your redemption value exceeds that. RTW business class redemption should yield a pretty decent value.