Was a professional animal trainer/zookeeper for past 15+ years, but by no means claim to be an expert on this breed.
However, I just wanted to say *PLEASE*PLEASE* do not under-estimate the the dangerous potential of this situation.
Make human safety the #1 priority, ESPECIALLY until you have the Trainer there, face to face, for evaluation. You were very smart to contact a professional, IMHO it is the ONLY option if you are even remotely considering keeping/rehabbing this dog.
I am by no means saying it is hopeless, I'm not there, so don't know... but there are a lot of SERIOUS red flags here, and this is a breed known to be pretty "hard core" with high potential for aggression. When you add in unknown genetics and a history of abuse, well... that's about as challenging (and potentially voilatile)as it gets.
Can you call the trainer and speak to her further, for any advice/suggestions (especially human safety related) to get you through til the 29th?
I hesitate to give any specific advice, but Karen Pryor's book "Don't Shoot The Dog" was required reading for all of my students and interns; it is a great introduction to positive reinforcement behavior management thru "clicker training". Ask your trainer what she thinks of it. (?) I am by NO MEANS suggesting you use this book as a substitute for a Trainer (!!!), but it may be a good "jumping off point" for you and your family.
Good luck!!!!