A great little booklet for Separation Anxiety is by Dr.Patricia McConnell (she's a well known animal behavioralist, author, and teaches via positive reinforcement)- the title is «I'll Be Home Soon». (dogingtonpost.com)
Dog trainers and veterinary behavioralists typically categorize aggressive behavior based on context. (puppiesdogs.org)
Your veterinarian or an experienced dog behavioralist, can tell you if your pet is a candidate for being re-homed. (homewardonline.org)