A clone would be far more impressive than a painting.
"Look there's Bishop! He's, like, awesome at robots and cloning!"
I think we have strayed from the topic here. I appreciate that you feel you have answered the cloning question in your own mind with what you believe to be the facts. However, you seem to be taking a rather self-important stance, stating that it's all been covered by your wondrous essay. I continue to believe that the only actual fact is that he still could possibly be a clone, as nothing in the films state otherwise.
And my opinion on the original question is that his emotional outburst points to him being human. Even if he was a droid programmed to look and act human, with human emotions, screaming "NOOOOO!!!" when it is too late to change Ripley's mind would be pointless and illogical.