Seems like a rather elaborate plot for Pinkerton's to get Gillian. And her arc mightn't be done yet. There might be more for her to suffer. Didn't quite a few states still have the death penalty back then?
Chalky was looking for an out even if he mightn't have realized it. Maybe as a younger man he dreamt of having and achieving certain things, but when he finally had them it wasn't what he thought it would be. In truth that happens to a lot of people whether they're good or bad. Also the problem with making it up the ladder no matter how secure you think you are there's always someone looking to knock you off.