you've got some strange shapes going on in the texture, notably the lips/nose area and forehead, and everything feels very undefined except for the eyes, which are very sharp and bright. can you post the diffuse?
In my opinion, it looks like there is a light just above his head instead of the light source being from his head. I dont think there's a lot of refs of glowing skin but maybe if its mnore localised, a diffuse soft edged halo or something, kind of like its glowing into and through the skin thats closest.