30# is light,, but I believe it will do the trick on a deer, as long as everything else is right. A friend in TX told me about his son getting a pass-though on a hog, pulling less than 40# (low to mid 30's, I think). It wasn't big hog--less than 100#--but they are a lot tougher than deer.

Too much draw weight can do worse than just discourage him--it causes shooters to develop some really bad habits, that can be really hard to break. Target panic is probably the worst thing that it could cause. You want to be comfortable and in control, and enjoy shooting. If you have those three things, it will come together a whole lot faster.

I don't mean to over-simplify, but I'm not really that good at explaining. Bow length is determined by the draw length and bow design. Generally speaking, a longer bow will be more forgiving and may be smoother to draw, a shorter bow will be faster. Other design features come into play as well. You want to get the happy medium of good performance, but a design and length that is forgiving to shoot. Go too short, the bow will stack, be picky, have finger pinch, etc. Too long, and you just loose performance without gaining anything.

Basically the limbs will only flex so much. They will get to a point where they go from picking up 2-3 pounds per inch to 4-5 or more. This is called "stacking". Limb design dictates what length bow can handle a particular draw length. To know what length is best in a particular bow, you will need to talk with someone familiar with that bow--the bowyer or an experienced dealer preferably, or somone who shoots that particular bow and knows it well.

Hope this helps--sorry I'm not better at explaining.

Chad