When do you stop getting disgusted?

Me and DH have spilt 50/50 custody with his 4 yr old daughter. We’ve been together 3.5 years. BM is the embodiment of the word “lazy” . She feeds SD bad food, she lets a device watch her, made her sleep on the hard floor, has told her she doesn’t want a daughter etc. SD has extreme anxiety about what day it is because she is so worried about going there. SD always vocalizes not wanting to go to her house, hating it there and wishing she could live with us full time. I operate the exact opposite as BM and SD definitely has said more than once she prefers me over BM. Everytime it’s exchange day I always feel immense emotions but one that typically resurfaces especially when my SD is talking about BM and disliking her or any of things she experienced throughout the week. Is a huge amount of disgust for DH. Disgusted he would impregnate somebody who doesn’t care for their child, doesn’t seem to want their child, and is just a bad mom overall. I just can’t understand how he could have done something so irresponsible and gross imo. I love being a mom and parent. I’m pretty anal about how I feel people should be parenting but it feels like no matter how many years go by I’m always going to have this strange fragment of unattractiveness to my husband because he made a poor child have to have so many traumatic experiences because of his thoughtless, reckless behavior. He was 17 and clearly he wasn’t using his head or thinking about the consequences and he needs to live with the choices he made but I still can never seem to get over it.