As FTL you'll receive additional 25% with M&M, so from BRU-FRA you'll receive 2500 and then real miles flown x2 + 25% of real miles flown to BOS for
10735 for one way. BOS-ORD is real miles flown+25% (don't know if those will be double or not in Z).
I believe that you'll get more miles with M&M (north of 21k) then with A3.