I assume that 35 kW is for the backup tower, although the question remains why
35 kW? Did the FCC limit the power because of interference caused by high
angle radiation ...


That is the consensus view ... the high-angle radiation towards co-channel
stations with the short auxiliary and 35 kW was about the same as with the tall
main, and 50 kW.

I guess under a CP case, a Class A is no longer allowed to increase its signal
towards a station of lesser class [ * ] .

Under the old rules, a Class A could not increase its signal towards a station
of the same class.

For this situation, WSAI had to install a DA which protected WWKB/1520 and
ZNS-1/1540, to about 40 kW. Before, it sent more than 50 kW towards those two
Class As.

[ * ] Look at WOR's CP DA ... it must provide substantially greater protection
to CKVM, and CKVM has been dark for some time, although it is still notified.