OP: Your sentiments after your test drive mirror those of many of us long-time BMW owners: The F10 is not as much of a driver's car as the E60.
And you missed one very important variable. You originally said you were considering RWD, as a modern RWD vehicle with dedicated winter tires
will handle as well (and safely) as an AWD with A/S tires
in almost all situations. I completely agree, plus the staggered wheels on the RWD's look great. We almost got a RWD, but... The absolute deal killer for us is the RWD 535 / 550 has electric power steering, while the xDrives have hydraulic steering. The vague numbness of the EPS was enough to push us into the xDrive camp.
I am guessing that 90% of all F10's sold in MN have xDrive, so it will be very difficult for you to test drive one to compare. But it is a critical data point - find a CPO RWD F10 somewhere and make sure you drive it before placing an order.
PS Your salesman is clueless. The 8 speed transmission is fantastic, and not at all responsible for the F10's feel. The steering feel and floaty suspension are to blame, not the tranny.