Hey dave,

Nice start. There are a few proportional issues, nothing too major. The size of your models cranium is too small. It should be in equal mass to frontal mass (face). This is just a general proportional reference, but it helps in nailing the general shape.

Your ears also look a bit too high on the head, the top of the ears should be level with the top of the eyes.

The general proportions of the face are as follows:

With a male head (frontal view). The eyes generally sit about half way down the face. Sometimes higher depending on the individual, especially with males.
The bottom of the nose sits half way between the eyes and the bottom of the chin. The mouth lies 1/3 of the way down between the nose and the bottom of the chin. The head is five eyes wide. Generally you should be able to fit one eyes in between your models eyes, and one on the outside of them. There are other 'rules' but those are the most important ones.

It looks like you've nailed a lot of this, but it helps to memorize it. And also to compare it with your reference, to see where it differs, as, no doubt, that will be a key feature that needs to be done right.

Your model looks like it's lacking a bit of form, in the jaw, and in some places on the face (Chin, cheeks, etc). I would stick to a lower sub-div level until you have some more of the forms refined. But generally it's a nice sculpt.

I would also post your reference, as it will make it easier for people to crit your model.

Really nice work Dave!