Thanks very much, it is a lot more readable now.
The ports and pins for the TX/RX leds should be swapped. The LEDs themselves are in the correct order (ON,L,TX,RX) but the ports and pins should be in the order D13,D73,D72 ; B.27,A.21,C.30 ; 68,107,103
About D77, what I meant was if you plugged your own LED (and resistor) into D10 on the board, Blink will flash it when led=10 or led=77. It isn't connected to any LED already on the board.
There are some other pin number oddities in arduino_due_x/variant.cpp, for example digitalWrite(79,HIGH) will set both pins 70 and 71 - I don't think it's helpful to add these to the diagram though.