I have had those moments: 'the N wins'. Those are really dark, and in your situation I can see how that must look.
I find myself seeking other ways to look at in your situation:
I have a child, and I know what it is to feel love for this person, isnt that one of the privilages of being trully human? I have, in my disfunctionalness done things when he was little that were terribly harmful to him, and I live with the pain of regret, I guess this is the other side of love. If your NM was to ever come to, and realise how she is behaving to the most valuable person in the world to her, her child, - I wouldnt like to be in her shoes, and if she never does wake up in this lifetime, (and it sounds like she probably wont), then this is even worse, she, unfortunately didnt really make it as a human. Probably in some deeply hidden part of her she lives with this knowledge ~ not sure about the 'winning'.
However one looks at it, you seem to be handling what you have to with great bravery, clear sightednss and courage and decency.
On a practical level, is there a way to handle this without having to let her have control? like suggest you dont tell her about your household finances but accept the money on a monthly basis, if that is what you'd like to do? Or what are your feelings about NC?