820-02098 5V

Board had corrosion around C7700 yes I got 2 of this Macbook with same area corrosion.

My question for this one is simple, U7700 was shorted replaced it but R7702 lost it pads and a new one cannot be soldered without some extra wire work, will that resistor for the line SPMU_IREF keep the Mac at 5V 0.045A and even DFU not working?

Not sure, R7702 establish some current reference for the SPMU; it may be important.
If you have working board, you can check what happens if that resistor is removed.