Well, if I remember correctly you have been trying to socialize him. Has he been around other people/pets much?
I would start out very gradually - maybe introduce him to one or two new people at a time and let him get to know them. Try to start with someone you know loves animals, and knows how to approach them. Since Cooper seems to be very shy, he needs a very low key approach. They should approach him quietly and slowly so as not to frighten him. I would keep the visit short, gradually allowing longer contact, and adding different people. Let Cooper's behavior be your guide. Trying to force things is only going to make matters worse.
I'm not an expert or a trainer - I just know what worked for me with my rescue chi, Tia. She had been abused, and was terrified of people. I had to first win her love and trust myself, then very gradually introduce her to other people/pets. It took some time, but it did work. You have a head start in that Cooper has not been abused and has been in a loving environment. As usual, patience is the key.
I have known a couple of chis that were nervous and afraid, and never learned to socialize well. I doubt that is the case with Cooper, but if it should be, just love him and let him be himself.