Hi Mark, sorry for the delay - so for your weight and kitefoiling experience, you should be able to learn and progress on the 5'4", as you are used to much smaller boards for sure in kiting. In fact, once you are better at winging you will probably move down to a 4'8" or 5'0", but that might be a bit too small for the first months.
Wing - 5.0 is good, no need for a 6.0 with your weight/foil experience. I'd go for the high aspect, usually only reccomend the standard Aero for SUP or Prone surfers or Wingers who are extremely wave riding oriented, although personally I prefer the HAR also in the waves due to the stability. 1500 is good, you should have the pumping technique already worked out for lighter winds, and 1500 is our riders (mine too) favourite foil! good luck!