Ann - you did what many many people would never think to do or be too scared to do - Take in that`little doll.
It seems after reading all your posts that she must have gotten loose or was left behind/abandoned and that makes it even more special that you saved her.
I would think her trust level would be ZERO if she had been abused and the scars and injuries could be from her being out in the world trying to survive or maybe she was attacked by another dog ....considering her head injuries it very well could be from fences. But as far as 'bait' I would think that would show also. (how anyone could do that to an animal makes me sick to think of)
She must have known at least a little love by humans or she'd be scared and untrusting...they do remember and it would show in her temperment
She's a lucky lucky dog that you found her and not someone else. There are so many dogs that meet fateful ends especially when homeless.
All the best and good luck with whatever decision you make. She's going to have a great life thanks to you.