Have you ever had him evaluated by a behaviorist? Before putting a dog on a med like Prozac, a full medical eval should be done and ideally a behavioral eval. Medication alone is not going to change his behavior (in my opinion). The only "trigger" I see mentioned is the dog walking issue. Sounds like he gets over stimulated and just bites whoever is there. Of course, there could be other triggers.
Note: I am suggesting a behaviorist, not trainer!! You want to figure out his triggers and work with them. While looking for a behaviorist, you might want to start working with him on basic commands, if you have not already. Take him in a quiet room or in back yard and work with sit to begin with, giving him treats when he gets it . After that, you can work with shake and down. Real basic commands that he will enjoy.
As for night time, for now I would put a soft muzzle on him so he cannot bite you. He needs to know you are in control, not him. You want to do that in a way that is not threatening to him. When he is behaving well, give him a treat and praise him for being so good!
There is a couple of books that may help. They are written by Tamar Gellar.... One is "The Loved Dog" and the other is "30 Days to a Well-Mannered Dog". She is very much into positive
Her website is:
www.theloveddog.com
I have worked with biters over the years and what I found was that the respond well to positive reinforcement. It takes baby steps but in the end it is so worth it to have a happy pup.
Please keep us posted. I wish you good luck with him!