I think those parameters are exactly what you think they are.
Not so long ago I was playing with porting Unreal’s PBL into Unity engine, and results were quite OK. You may want to make sure that your dot products are actually wrapped with max(0, value). Also try to keep your specular parameter bigger than 0.1 and smaller than 0.9. In my case I had very weird results when specular was 0.
Also check out this blog post, if you haven’t already:
Cheers!