I definitely agree $50/week is plenty. I graduated two years ago but I was probably in the $30-40 range. And if he has a job I would definitely consider cutting him off completely after a semester or two.

Going on plenty of dates is definitely a good thing. And you don't have to go to dinner or spend a lot of money on dates. Obviously he'll need some money, but I would think it should mostly be up to him. Especially if you're also paying for rent or tuition.