OMG!!! What in the world!!! I would have kicked your ex bf from here to kingdom come!!
5mo is soooo young. Not that an older dog should be hit. He is tiny and growing!!! I am sorry I am so upset. It just crushes me! If I were your pup I would be barking at men too!
You are going to have to get him around males that you are comfortable with that are willing to show love and affection to him. Hopefully he will come around.
We picked up my lab, that my parents have now, when she was 6 months who was an outside dog and was horribly abused. She is skiddish to this day and is constantly seeking affection. We love her, pet her, play with her, and she is still scared to death. She is now 9 years old.