I have talked to a repairman and he says the control board never or rarely screws up on these type of diswashers.
The 7 flashes indicateds a failed heating system. You dsay that you have tested the heating system components (thermistor and heating element) and they are good. If that is the case then the only thing it can be is the main control board.
I have personally installe a few control boards in this type unit. They do fail and the 7 flashes is a common error with this model series.
As I mentioned in my last post if you get the parts from http://appliancepartspros.com you can return them if needed.