Greetings gentlepeople... I recently found myself in the same predicament at the end of the "Crush the White Legs" quest. Fortunately, I had made a save file right before the Joshua Graham/Salt-Upon-Wounds dialogue. The only way I could get the quest to successfully finish after choosing to spare Salt-Upon-Wounds was to use the console. Specifically, "setstage x008a36 100" (the value of x depends on where Honest Hearts is placed in your load order) did the trick. Upon using said console command, the quest completed successfully, the "Crush the White Legs" challenge was completed, all relevant xp was awarded, Joshua Graham's final dialogue started, the ending slideshow played and the "Departing Paradise" quest started. Keep in mind that if you are trying to unlock Steam achievements, using the console will prevent them from doing so. I had to finish the quest the violent way first in order to unlock the achievement, then go back to a previous save. P.S. I am currently running the Mission Mojave - Ultimate Edition v3.1 bugfix mod, but it seems to have no effect on this particular issue. I tested the above solution after temporarily moving the MMUE files out of the FNV folder and it made no difference.