Still digging around. Sure enough, after we opened things up last night and cleaned out the ice again, we powered back on and the R-FAN was reading 9V! So perhaps the 0V we were seeing yesterday was with all the ice/frost build-up. The other two fans C/F are still 9V, so all three fan motor/circuits appear fine.
Did some more measurements on the circuit board for the various sensors
R1 (R-SENS): refrigerator ambient/temp sensor was ~2.8V or ~34F
F-SENS: freezer temp sensor was ~3.9V or ~-8F
R-DEF-SENSOR: still 0.9V, when expected is 2-4V
It sure points to the defrost sensor being the culprit.
With regards to that evaporator assembly cover, I've been reading around, but still not sure if it includes the fridge temp sensor. In the parts diagram/list, it seems to suggest it's installed in the upper cover, or ASSY COVER-MULTI REF (#4). The evaporator assembly cover is ASSY COVER-EVAP REF (#3). In the parts list, the temp sensor is listed as #4-2, so I suspect it may be part of the upper cover rather than the lower evaporator cover: