you say that he took what he was owed. How did he do that? Did he open his wallet and take it? Sounds like something called demanding money with menaces, which even if he is owed money may not be ok in law. If there was violence it wouldnt have happened if they had not gone there and if the other person. Why did the other person panic? What were they doing to him?
You then say "my bf didn't even get his injuries properly checked out because he was considered a criminal". Why was he considered a criminal and who by? A hospital? Sorry this story does not make sense and it is unlikely that a jury of 12 people were all unable to follow the evidence presented and that the judge would give a custodial sentence lightly in these times of overcrowded prisons. My opinion of a successful appeal is that it sounds, based on what you have said, unlikely.