Is something wrong with her?

My daughter is 6 weeks old. I have 5.5 year old and 2.5 year old sons. Both were very different newborns. My oldest was formula fed, very fussy the first month but pretty quickly learned to sleep long stretches and was a good sleeper thereafter. My younger son was breastfed and definitely cluster fed a ton at night and co-slept until 8 months, but he did sleep well in between feeds and was easy to settle. They are now polar opposites. My oldest is on the spectrum (all language/communication issues, no other real behaviors. He's actually pretty easy going and passive, just terrible at communicating and social interactions). My younger son is super smart, precocious, very advanced with language and social skills. Our baby daughter is a terrible sleeper. She cries a lot and is hard to soothe during the day, and at night she is cluster feeding. But instead if falling asleep at the breast, she punks out and loses her latch after a few suckles, then starts squirming and getting distressed. It's been weeks of me wrestling with her all night, trying to get her to doze off or feed for longer stretches. Even when we have bottle fed, she still acts restless and doesn't really sleep. It's not a ton of crying, but more fussing and moving around, crawling all over my chest and kicking/squirming. My husband refuses to help much now because he can't breastfeed and she cries more when he holds her. He doesn't want the other kids disturbed, so he lashes out at me any time I ask for help. Last night he slept for long intervals while I yet again desperately struggled with her for 6 straight hours. He thought she was sleeping because I kept her quiet. He became enraged when I finally revealed my distress and he told me our daughter must be brain damaged. He thinks a 6 week old having these issues with sleep means she is neurologically impaired, or has autism. He is bitter about our older son's issues and told me if our daughter is also compromised, he will walk out. Ironically, he resents our middle child too even though he is bright and developing normally because he is "wild and demanding." I'm not sure if I should take our daughter to the pediatrician urgently for more evaluation, not that "brain damage" is reversible anyway. But I fear if I don't seek input and she grows up with issues, the blame will all fall on me. My husband wants a full neurological evaluation including MRI, which I'm pretty sure they won't do on a 6 week old for poor sleep at night.