Your best bet is to get him neutered and her spayed she is way to young to even take the chance on her winding up with puppies your dogs will be healthier and happier if you get them fixed plus she wouldn't go through heat every 6 mos and you wouldn't have to worry about unwanted puppies
If you just got her she is going to whine because she misses mom and her siblings give her time to get use to being away from them also she might not like the crate so take her out of it when my dogs was puppies I would put them in bed with us at night and they would sleep all night long plus...
My min pin has seizures and he will kick his legs and shakes I have to pick him up and hold him and let him and tell him that mommy has him when he starts to come out of it he will pant hard
Yes you should take one to give the poor little thing a chance for a loving home and a happy life and you should take it right to the vet and get the poor little thing checked out and he will be able to tell if it has fleas. Good luck also take the others along with the mom dog to the humane...