What do I do to fix this?

So, since I am a newbie at SEO and I tend to learn by trial and error, I thought I would experiment with Pinterest. I downloaded a bunch of photos that are directly related to my niche and uploaded them onto a single webpage on my website. Then, I gave all the photos a backlink to different pages on my website. I then used a plugin that prevents Google from crawling the webpage and, therefore, keeps the page hidden. Since I don't own the copyrights on the photos, legally I can't have them displayed on my website. I then pinned the photos with the backlinks attached to Pinterest at an average rate of 10 to 15 photos a day and I changed the source link that Pinterest always attaches to the pin to the backlink I had already attached to the pin myself. Amazingly, my website began to move up in pagerank (I believe because of the "social signals") and, of course, I was getting more and more visitors, and obviously, the visitors were being directed to the link I placed on the pin and not the webpage with the photos on it. That was all last week. Then in the past couple of days, I noticed my website was dropping about a Google page each day. I went from hovering around page three and four to page eight. I went to my Webmaster Tools account and there was an error message stating that i had over four hundred "404 Page Not Found" errors. Most of the errors were related to the Pinterest backlinks. I am guessing that this is what is causing my page rank to fall, even though Google says 404 errors don't affect your sites ranking. Does anyone else think this is causing the problem? What should I do? Should I just delete all those pins and delete the webpage and consider the experiment a failure and start from scratch? Or, should i use 301 directs?