Sure, you know what to do. You leave him or you stay. He sounds like he is addicted to porn. If you stay, you will have to deal with these issues in the future. If you leave, than you will not. The question should be: Can you deal with these issues in the future? Answer this question and you have your answer.
First of all, why do girls feel the need to snoop through their guy's stuff? Then, they get pissed at what they find. Giving him the benefit of the doubt, I don't think there's going to be a whole bunch of girls on webcams doing "unspeakable stuff" unless its a private webcam. In that event, not knowing yours or his age, what some of these girls do, inappropriate as it may be, is their business. Now, if the porn bothers you, then its not going to get better. However, does it bother you to the point where you can't tolerate it? In other words, I've been in relationships with women where I secretly find out that they don't mind porn and we've incorporated it into the relationship. Find out the root. Is it because he likes something he sees and isn't getting it in the real relationship (usually the cause)? If you still have a problem in a month's time, its never going to go away. Be honest with him and say, "I thought I could deal with it but I can't" and cut your losses. Keep us posted. I'll add this on my watch list.