the only problem with the way you do your hair is, it looks nice from the back, but from the front and sides, it looks sub standard. His hair isnt the easiest thing to model. Also the model could do with a bit of work, along with all of the hair forms, but it is certainly a good effort, dont get me wrong, theres just a lot of room for improvement, for example the legs and too square etc.
most of the visuals u could probably see whats wrong yourself, however, i wouldnt worry too much about the polygon limit in halflife, from my research you can do as much as you want, since its just limited to memory