I had a similar issue last year, although ticket prices were much better. Wound up going on a BA ticket in J (actually I or R) using AA for DFW-MIA and IB for MIA-MAD. Can't tell you how that worked out as flight times changed and BA moved me to AA36 direct DFW-MAD. Going through MIA certainly looked better on paper than ORD, JFK, or LHR.