Growling and lunging at family members

Question
Someone dumped a dog in my rural area (I brought it home)I took him to the vet, had him examined, immunized and later castrated.  We have three other dogs (inside/outside).  A month has past and he is settling in well except he doesn't want anyone around me, or so it seems.  He growls at my husband, daughter, + grandchildre.  He has never growled at my son-in-law or me.  I am going to take this 16# terror back to the vet to see if there is a physical reason.  I have felt it heart racing (150 BPM)for a hour, then will slow to the 70-80's.  Today, he was shaking all over, nipped at my husband, had a fast heart rate and vomited 30 minutes later.
If there is nothing physically wrong with him, how do I handle this behavior?

Answer
Hi, Sharon,

Thanks for the question.

You have to be very careful at all times with this dog until he becomes totally acclimated to living with you. He's essentially got PTSD. We don't know what happened to him to put him in this state but the accelerated heart rate followed by vomiting indicates extreme stress reactions.

Does he only growl at others when he's sitting or lying next to you?

Having your husband and daughter hand feed him and take him for walks will probably help. They should sit or lie on the floor when they feed him. No one should scold or punish him for his fear reactions to them.

I hope this helps,
LCK

(Let me know what the vet says.)