Around here, based on deer that I've sent for lab aging, that amount of wear on your jaw would be from a deer at least 5.5. Tooth wear estimates are based on looking at the dentine exposure, not on how much the tips of the teeth are worn down.
Your jaw doesn't look like that of an old timer but he most likely isn't a 3.5 year old either. Tooth aging is classified into a couple categories...Tooth replacement, which is a for-sure method up to 2.5 years old. After that, it becomes a "wear" estimate. At that point, you place them into age groups...middle aged, fully mature, or old age. Not many old age bucks are running around most parts of the country.