You should keep him. He deserves a better life.
Keep him, please! 
This poor pup needs you. He’s scared, but with time and love, he’ll come around. You’re doing the right thing.
If you decide to help him, make sure he’s warmed up first before feeding him. Cold dogs can have trouble eating.
Please call animal control as soon as you can. This kind of neglect can’t continue.
Your dad is right to call animal control. They’ll handle it officially, and you can report the neglect separately.
Take the dog in and call for a welfare check on the owners. Neglect like this shouldn’t be ignored.
Wyatt said:
Take the dog in and call for a welfare check on the owners. Neglect like this shouldn’t be ignored.
Sadly, even if the pet is neglected here in the U.S., you can’t take it without risking charges for theft.
Most shelters will give owners a set time to reclaim their pets before the animals become adoptable. If you do take him, make sure you follow the legal process to protect yourself.