As mentioned SEA-JFK isn't really memorable (LAX-JFK does have real F service on AA, but SEA-JFK does not and it is worse than QF J MEL-SYD for example). CX J YVR-JFK would be far nicer, and you may be able to get CX F awards (they do exist, just scarce). IAD-LHR on BA isn't a nice route (have you considered DCA-MIA-LHR-EDI -- much nicer flight in BA F than IAD-LHR with extra flight time and MIA is fun to visit). DCA-JFK-LHR is also a possibility (that gets you the great BA Concorde Room at JFK with real dinner service, again much nicer than IAD).

DXB-HKG is pretty grim, on RTW tickets I always book DXB-LHR-HKG and there are no UK taxes on transits (only for stopover). LHR-HKG awards are easy to get (served by lots of flights, incl. BA/QF/CX). J on RJ is pretty good, so IST-AMM-DXB-LHR-HKG might be the best way if the award rules allow it. That would get you 5 good F legs (vs. the 3 you have in the original routing).