I'd call it a slurve. That's not really sharp late break like a slider has, but it looks like he is supinating his wrist at delivery - which you don't do with a curve.
I am certainly no mechanics expert, but I'd get him to a pitching coach that can get his lower half involved. I know he was in the stretch, but he is throwing all arm. Doing that, and throwing a slurve isn't a good combination. You need to get the lower body involved more in order to lessen the strain on the elbow/shoulder.