The thing that bothers me from a Radio Hobbyist/Radio Historian perspective is that the Day facility with 35 kW falls short of the efficiency of a 50 kW Class I-A/A facility, being 1581 mV/m inverse field at one mile, vs. the Historical Class I-A minimum inverse field efficiency of 1591 mV/m at one mile. The Night 42 kW pretty closely matches most Class I-A/A inverse field.
Your calculations show a 0.1dB change in field strength, which is not even measurable with any reliability in the far field. The change between 50kW and 35kW is 1.5dB, the difference between 40kW and 35kW is 0.8dB, both of those changes are measurable. Neither difference would be audible in the field with an AM receiver's limiter above threshold. The change in facilities would be more interesting in terms of RF bandwidth performance, which relates to audio processing and received apparent loudness. It's entirely possible that the new signal will be louder, and perceived as stronger, but it will be arguably identical from a listener-perceived field strength standpoint.