I understand what you are saying, but is there documentation anywhere about this?  If you are correct, then what is the point of code "Q" for the dependents, which reads "Not a dependent (but is a qualifying person for the earned income credit and/or the credit for child and dependent care expenses"?  It seemed to me that code Q exactly addresses what I was trying to accomplish.

Further, I can keep the mother's return with code Q and Form 2441, and file the father's return without Form 2441, in which case mother would get tax-free dependent care FSA, and father would get CTC and HoH status, so that's a scenario where both parents are getting some sort of benefit for the child (counter to your statement that "Because the parents are living together, only one parent can claim ALL benefits for the child."

Appreciate any further insight anybody can offer.  Thank you!