Make sure you have the canonical tag in the header of all your pages. It helps Google tell what is the original source of a page:

https://support.google.com/webmasters/answer/139394?hl=en

Also, check in webmaster tools to see if your site has a manual penalty, being penalized can cause other sites to show up higher than you in the SERPs for your content.

Interesting. Google is usually smart about not indexing proxies, but here it looks like it's doing exactly that.

You can try using Javascript to break your site out of any frames when a visiting your site. This will break the user out of the frame if they come via the proxy, and may also help prevent Google from indexing the proxy frame:

Yes, that is a good solution, especially in this post-Panda world. Ideally you would just have one page for Bic pens, with a drop down from which you can select different options such as colors & size. If your shopping cart system doesn't allow you to do that, then the canonical is a good approach. This cuts down on the amount of duplicate content you have and the amount of unique content you need to create.

If you want to rank for "flat head screw driver", the canonical approach can still work. Simply create a landing page for flat head screw drivers, and include all of the flat head screwdriver products from each of the different brands. Then canonical each of the individual product pages up to the main landing page.

Yes, I've used this approach for a number of ecommerce clients, and it is very effective. There are many advantages to this approach:

• Eliminating duplicate/thin content across the site
• Focusing link value on a single page instead of spreading out across multiple products
• Less effort creating unique content (one page vs multiple)
• Potentially better user experience

Of course, if you have the resources to write unique content for each of your product pages, that is going to be a better solution. You can still create a landing page in this instance, you just wouldn't canonical the product pages to it.

The question mark and the values that follow are known as "query parameters" or "query variables", and they actually can impact your SEO. Google can look at the different variations of the URL, and index them as separate pages, leading to duplicate content.

The easiest fix for this is to put a canonical tag in your header, so that Google knows the what the proper URL for the page is supposed to be. You can also tell Google to ignore specific query parameters in Google Webmaster Tools under Crawl > URL Parameters.

I would check in Moz Analytics or Google Webmaster Tools to see if there are any new 404 errors to ensure that the 301 redirects were put into place properly. It could be possible that not everything was redirected properly.

I would also look at the indexation numbers in GWT as well as run a site: search in Google, to see if any new pages have been indexed. Wordpress tends to create a lot of duplicate content pages such as category archives, tag archives, date based archives, author pages, etc. so make sure those aren't being indexed. Use a All-In-One SEO or Yoast plugins to clear those up.

Finally, go into Google Analytics and look at the landing pages that were driving the most traffic before, and compare it to after the change. You may be able to isolate a few high traffic pages that are responsible for the traffic drop.

If none of those things turns up a problem, don't panic. 4 days is not a long time and an 80% drop is not unheard of. It can take some time for Google to digest all the changes, depending on the size and authority of your site. Make sure to submit your site to be indexed in GWT under Crawl -> Fetch as Google. You can also speed up Google's crawl by building more links to your site. Twitter, Pinterest, and Google+ are all easy ways to get pages crawled and indexed, as well as getting links from high authority sites.

You may find this case study helpful of a blog that decided to exactly that:

http://www.koozai.com/blog/search-marketing/deleted-900-blog-posts-happened-next/