Union officer musters out, returns to NYC. His wife is spoiled brat of banking family. They get screwed by her mother and brother. MC leaves and heads back to Virginia. He buys a horse, rescues two black children and a young white kitchen helper, ends up at the horse's old home where he helps the widow lady.
Unfinished but a great story. Any ideas?
Sounds like A.A. Nemo's 'Amends.' Currently unfinished, as you said.
https://storiesonline.net/s/65451/amends
https://storiesonline.net/a/a-a-nemo
Without re-reading that A. A. Nemo story, I'll assume it is the one you are looking for.
Another very good story - but definitely not the one you describe - is https://storiesonline.net/s/21394/a-perfect-she-devil by Todd_d172, although the MMC is from Boston and unmarried at the start of the tale.
Yes! I just reread that one. Just reread his Tales from the Shack series. Highly recommend.
If you had not known about that story you had probably not discovered that author. He's great, although I sometimes feel his works could be described as "Gun porn".