Please recheck the FLL-MIA segment logic. Are you able to get this counted as a co-terminal or are you being assessed this segment as a ground segment? If this counts as 1 of your 6 NA segments, it serves no real purpose and could be better used elsewhere to accrue miles.
IIRC FLL-Mia are about 25 miles apart, so easy to fly to just one city from DFW and do whatever you want in the other and return to DFW from the city you arrived at. There is very frequent service DFW-Mia, so would suggest that routing.
Also, not sure why you are routing EWR- LGA-DFW-FLL-MIA-DFW-LHR. Again, you may be assessed a segment for EWR-LGA. Better to find a flite to/from only one NYC location.
Also, why two passes thropugh DFW? May be better to route NYC-MIA-DFW.
Finally, looks like you may have 7 NA segments, but this can be easlly reduced as mentioned above
Sounds like a fun trip. Enjoy!

Rens