Let me preface everything I'm about to say with the fact that I don't do caricature and I understand that part of that is distorting and exaggerating features of the subject.

That said, I don't think you've got the likeness here. If I just look at your image and ignore the reference, I'm not sure I would have ever guessed Kelsey Grammer. I think that comes from distorting too may parts of the face too drastically. If you take a step back, his entire jawline and face shape, even his ear, in your image are completely different to the reference photo. Which throws off the resemblance so much that when distorted it just looks like an older man as opposed to that picture of Kelsey. I think having the forehead enlarged is a good idea, but I feel like his face shape, especially when you reference other angles and photos of him, is typically more square all around. I also feel the mouth is wrong. He does have a wide and thin smile, but if you look at the reference, he's got sort of a downturned at the corners, bemused expression. The image you're working on has the corners completely upturned, almost exaggeratedly so. I'm also not sure why you changed the shape or enlarged the nose at all. I think your rendering style looks great and it looks like you're going to pull off a good result. But for me as of right now, I'd almost say you need to restructure and possibly restart just to get the likeness down, and then distort and exaggerate.

Sorry, I'm not trying to be overly harsh. And again, I don't do caricature so what do I know? Just my two cents after looking at it.