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Couldn't have said it better myself.  This is exactly the correct answer.

If the redirect to the testing site actually is temporary, this is one of the very few instances I would recommend using a 302 redirect.  This way, the engines will understand that you aren't making this a permanent move and will, hopefully soon, remove the redirect when the staging site goes live.

Definitely do not worry about the disavowing nofollows, unless the domain itself is somehow egregiously offensive to your brand.  Otherwise, you're safe to stick with dofollows.

Very simple.  Find your .htaccess file  for the URL you want to redirect FROM and add a line like the following:

Redirect 301 / http://www.example-site.com/

Just change out your own destination URL of course.  Don't ignore that solo slash, that's key as well.

Google is location-agnostic, though will act like it cares about location depending on the location of the search.  If it pulled the wrong thumbnail for you, it got there via a link (internal or external) and felt that is an appropriate result.  What you do now depends on your goal (change the thumbnail for example).

It's good that you appear with a geo-targeted piece of content.  This means you're responding to local searches.  Google will show different SERP results for every person and location, so there isn't much value/concern over how they see your site.  They see it from "all" locations.

In my experience it can take a while to see sitemaps updated, particularly if you are a small site and are updating it daily.  Unless your site really is changing everyday, I would submit it less often and/or just be patient.  You didn't indicate how long you've been waiting, but at least a few weeks to a month or two if your site is new or "small".  If there is a problem, your Webmaster Tools will let you know.

I agree with Crusader as well.  Sections should be broadly included in the sitemap...specific individual pages aren't really a concern with this (assuming you link well to them).  You are only meant to provide the structure of the site to Google (main section, sub sections, subdomains, etc.) and let them come index when they are ready.  But I do think you probably need to move onto other efforts and be patient for Google to get around to visiting your site.

If you are using rel canonical, you're doing it right.

The real question is why that second link exists.  Somewhere on your site you are linking to that snap-picture-poster-frames subdirectory.  I would spend some time figuring out why that is the link and not the direct canonical link.  Then fix it.  It's unnecessarily confusing and points to some poor site architecture.  Removing it will both eliminate the dupe problem and also just leave you with a cleaner link structure.  Being in two categories shouldn't mean you need two different URLs for the same product...

I've never encountered an official limit to image filenames, and I'm not sure there is any SEO impact (other than just the engines ignoring alot of the filename in their crawl).  Putting the product description in the filename seems VERY unnecessary and I would try to get some rationale around that.  But for the web usage overall, I've never encountered a filename that is too long.  50-70 characters is alot but not prohibitively.

So if you have to FORCE the engines to prioritize one of multiple duplicates, you have a few options.  Assuming you want both pages to exist, you can provide a nofollow or noindex rule to one of the duplicates.  This is a blunt approach which works well but not really the coolest.

The coolest option is to give one a canonical tag.  Telling the engines that one of the multiple duplicates is the "canonical" one is what Google even recommends (and it has all sorts of neat downstream SEO benefits anyway.

So add a "rel canonical" tag to the "proper" page.  Matt lays it out here:https://support.google.com/webmasters/answer/139394?hl=en

Let us know how it goes!