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Most blog platforms offer the ability to not index various conglomeration pages (category, author etc.) I would recommend using those options so only the actual article page gets indexed.

I worked on a similar problem, we created an interstitial page for a general product and then used canonical tags to point all of the e-commerce product pages back to the interstitial page.

Ideally you would want one page where you could just select different options, but depending on your technology that may not be possible.

The first question is why are you going to have many stores doing the same thing, is each one unique in some way? 
Without more information as to why you are doing it this way it is hard to help with the best way to handle it.

Some CMS would do that automatically, if the company you are working with had one of those (or the decision maker is used to seeing that) they may just think that it is normal and a best practice. At the end of the day, while odd now, it should not matter from an SEO perspective (just make sure that you redirect the base url to that page).

Why would you worry about SEO on pages that targeted? The only people you want finding them are the specific companies, I would no index all of them and use the best versions of the copy to create a few general landing pages.

The function of the meta description is to provide a snippet for the search engine to display, it is not a form of masking, that site is using the meta description for its intended purpose.

http://www.wordstream.com/meta-description

I think you are asking a large, loaded question.  I do not think there is a "yes you should" or "no you should not" answer for your complex question.

This content is upwards of nearly half a decade old, is it still relevant?  Instead of a blanket yes or no, I think you should go through all of it and see what is still valuable, depending on your industry it could be half of it, or it could be none, but you should be looking at each piece individually, not the entire site as one whole. For moving it, if the content is good I think placing it on your site (as I assume you want to consolidate) and redirecting to the new location is fine, plus if you do it as you go, you will not have a massive surge in your content, or drop in the old site but a gradual shift over a period of time.

Hope this helps.

Brian,  a 301 is a permanent redirect, so while you have turned them off the link has already been associated with your new domain.  I would recommend reinstating all your 301s so that any legitimate traffic going to any of your links gets to your new site and then go through and disavow all of your spammy links. In general, when you have any spammy links you should ask for their removal and then disavow them if they are not removed while still creating 301s from all of your old pages for both legitimate links and traffic.

That will all depend on what CMS you are using and how your site is built.

If you are generating pages dynamically in your e-comm then yes you will want them to have static URLs, along with all of the proper formatting and parts just like any other page.  There is nothing wrong with dynamically generating pages as long as you still follow the rules.  If your generation creates multiple variations of the same page/ page with similar content then make sure to use canonical tags to point each group to one static URL.  Lastly, do not worry about creating more pages, worry about creating relevant and useful pages/content based on what your customers are looking for.

Sorry to bare the bad news, but without being able to set up redirects you are out of everything you had besides the actual content that you can put back up.  All of your link power is gone, you won't be able to get any historic, in general you are starting from scratch but with (hopefully) a decent amount of already tried and true content.

A missing title is your meta title, it is the words you see in the tabs on your browser.

H1 elements are in your copy, each page should have one, and it should be the main focus of the page.

We use re-targeting ads for cart abandonment, the company we use is conversion pixal based so there would be no issues with your customer CMS.

You are moving the wrong way, Google has said that they prefer sites to be secure and that this will be a factor more and more.  As per your question, yes if you create 301 redirects your SEO losses will be minimal (and don't forget to update your GWMT).

All you will need to do to fix any problems from a search perspective is create a canonical tag that points at your preferred home page and place it into the meta on your home page so it will be shown across all variations by the CMS.

If you have a website with over 10,000 pages that is partially e-commerce then you should not be afraid to pay for a proper solution. Free is great when you are starting out but there comes a time when you need to invest money (and it will be a small amount) in the proper tools to continue your site's growth.

While you might see a small down tick in the beginning as Google indexes and updates, overall you should not suffer any long term negative effects from standardizing your URI structure.

Also, your Google traffic and your Adwords will never line up perfectly due to the difference of how each is tracked.

Google has gone into the differences here:  https://support.google.com/analytics/answer/1034383?hl=en

Did you link your GA and Adwords accounts or are you just tagging?  Organic (not provided) is how GA shows all search traffic from users who connect to Google securely (signed into a Google account) so this could be branded traffic but there is no way of knowing in GA.

Just because you rate well on Bing and not Google does not mean you are being penalized.  Bing uses a less sophisticated algorithm compared to Google so different tactics (older ones) can rank you higher on Bing.  Just keep doing the right thing with content creation and adding value to your site that people who use the word "sensaphone" in a search will find useful.