Would the size of the penis determine the amount of testosterone produced? I'm 16 and I hardly have underarm hair and facial hair. Would it be bad for me to take zinc to boost my testosterone levels?
Your genes determine the size of your penis. Testosterone is needed to activate the genes for male traits, such as facial and body hair and muscle growth. However, extra testosterone won't change the size of the penis or cause you to grow hair that you normally would not produce. Nor does the size of your penis indicate how much testosterone you are producing. Testosterone, by the way, is produced in your testicles.
If you were deficient in the amount of zinc in your diet, then taking zinc would increase your testosterone levels. However, most people get plenty of zinc when they eat a well-balanced diet. Taking more zinc than you need won't cause you to produce excess testosterone. Your body has numerous checks and balance systems to regulate the amount of hormones in your bloodstream.
Few guys need to boost their testosterone. Your lack of hair is solely due to not having reached that point in your development yet. Most guys aren't able to grow full beards until they reach their mid-twenties.
Masturbation by itself is neither right nor wrong. See: I'm still confused about masturbation. Is it right or wrong? If you use pornography or thoughts about having sex outside of marriage to get yourself aroused enough to masturbate, then that is wrong -- not because you masturbated but because pornography and lustful thoughts are wrong.