i'm very sorry for you and i can personally relate to what you are going threw.
i bred a few times. my daisy had two kits and they were doing great, and at about three weeks old one of the boys had the rectal prolapse [like you said above] i rushed him to the vet and when they put it back in, it wouldn't stay in so i gave them the okay to operate. when they opened him up, he had tortion. he had to be put down.
no ryhme or reason.. it just happened.. i cried so hard.... so i just wanted to say i'm very sorry and sometimes there just aren't answers and i don't mean that to sound rude in any way at all.
jean