Your evidence can be admitted at trial with a proper foundation. To understand what that means you really need a lawyer. At preliminary hearing the defense is limited to affirmative defenses. I've always wondered what exactly this meant and if it limits the defense from directly contradicting the victim's evidence. As a tactical matter your attorney may not wish to show his hand at this stage. As for your attorney you should be asking him these questions, not a stranger on the Internet.
There is nothing in what you have provided that would explain why the video wouldn't help because person who taped it would be tainted witness. Nonetheless, your current attorney would be in the best position to judge that issue.
Explain this to your new attorney. It can be used as the other posted mentioned with a proper foundation. That means either the man in the video has to admit is was him at the time of the filming, the person filming would have to testify. Do not do this alone under any circumstances.
The above information does not establish an attorney client relationship nor is it meant to provide legal advice.
How does all this help you? In a felony VC 23153 the injury can be ANYTHING. The amount of injury may have to do with the sentencing and restitution, but contesting the degree of injury at trial will do nothing for you. You are not concentrating on the elements of the case that the DA needs to prove. Discuss this thoroughly with you current attorney.