Hi Shulem,

I think you have great qs & for many of them bothered me also. Here is my answer: 

1. Looking at the opposite sex for men is normal, only problem is from religious prospective.  So if you were not frum (non-Jewish), occasional looking at porn /masteterbution would be 100% okay.  The addiction comes in is when one has trouble stopping  engaging in these activity when it impacts their day to day life. 
2. I think you might have problem with loneness.
3. I think Yeshivas / Jewish day schools are horrible at sex education. I went to a modern orthodox days school & we have just 1 half hour class about it sophomore year. Even halachic things like niddah / shomer negiah  were never covered. I have to learn about those things by Googling them. One of the reasons I started to look at porn, was I due to searching the web about sex, since I knew almost nothing about it and did not want to be in situation where my future wife would be more knowledgeable about it. I do not understand why you can not ask  your wife about wearing difference things?
4. I am unsure where it’s in Gemora, but it talks about the fact that Sahndrin made it so that lust for avoda zora went away & it did. Then they tried the same things for sexual things & world stopped functioning, so they restore it. So I would yes to your question. What keeps me going  is the fact that most of the Jewish leaders had problems with this stuff (Yehuda, Samson, David & Solomon) & we are just stam yids! So what does Big Man from upstairs wants from us?     
5. That is a trap. In the beginning , I would say the same thing & tell myself there is no issur to look at the woman, but only problem is masturbation & in fact in the beginning I would turn off the computer when it would get close to that point, but after while I just could not stopped watching & masturbating.
Good Luck!