I don't know why you have different mileage totals. A redemption to KBP will be 75k points round-trip (with up to 2 en-route stopovers or an open jaw), although it can be broken into 2 1-way segments at 50% of the point value.

https://www3.aeroplan.com/FlightRewardChart.do

Basically you've found a few itineraries with very low surcharges, particularly August 9/11/18 - August 31, for 75k points and ~$80. Which is pretty good avoidance of excessive surcharges.

Since you have plenty of points, don't need the stopovers, and the surcharge is minimal, I'd suggest redeeming Y in the outbound, and Business on the inbound.

Good luck!