Oh my dear dear, you have lot of misconception about masturbation. It is normal physiological urge and act (please refer my other answers about masturbation). It is what you do in female’s sex organ (vagina) is you are doing in hand. In other words it is intercourse in hand. How come it is harmful if intercourse is not harmful? Do you have any logic to prove your point? It is not harmful at all, except if it is compulsive. Some of the men may develop premature ejaculation because of this habit as they train them to ejaculate faster. Size and angulations has nothing do with it, in fact angulations is normal. Your anxiety over masturbation may be the cause of weak erection. Get relax and stop worrying, nothing will happen to your sex life because of your masturbation. As far as your wife’s satisfaction is concern, it is not your size but your love, affection, concern and respect you hold for her is more important.