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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.

So you are asking on Moz if you should steal content from Moz then not credit them to increase your search ranking, and then your concern is not if what you are doing is wrong (it is) but only if Google will penalize you for it?  I believe that if you want content for your site you should make it or pay for it, not steal it, if you write optimized content then maybe people would expect copy on your site to be written by you.

Write as much copy as you need to convey the information that is needed for your visitor on that page.  If you can create a good user experience on one page with 100 words (by answering the pain that they would be going to that page to solve) and then you need 1,000 words for your next page, then do that to.  Don't make arbitrary copy limits or goals based on SEO, make your pages user friendly and your copy useful and your pages will rank well for the appropriate content.

While they as a whole have high page authority, when you create a sub domain blog on them, it does not get the same.  You should worry about creating good content on your site instead of making free blogs to put content onto to then push to your site.  Your best bet would be to set up a blog onto your website so that you can have new, relevant content being consistently added to your site.

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).

You should disavow those links, if they are not effecting you now, they will eventually.

As for why you are not back to the top, you changed your site's focus so you lost all of the historic "mojo" that you had for those keywords.  Even now that you have put them back, what was lost is gone, you will need to slowly, overtime rebuild to get get back to what you had before.

If you cannot dedicate the time to SEO, bringing in a professional may be your best option.  They can help you get on the path to recovery and work with you to hopefully improve past where you started while fixing what this other company did.

Yes all of those can negatively effect your ranking.

I would guess it has to do with a lack of any actual content on the main page, and all of the other pages "content" being aggregated from other sites where it was originally posted.  A site like this would need either a large amount of advertising to drive traffic or in my opinion a complete overhaul and reevaluation of the content strategy.

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.

While you should not fear change, your comment "However, the current setup is sending a worthwhile traffic volume to the site." says all you need to know, if the service + city landing page model is working, don't change it to change it or because you read something that says you should.  If you do however believe that targeting the broad keywords instead will net you better local results, set up a few landing pages for the broad keywords and A/B test them against the local landing pages.

That is pretty odd that you are not getting traffic from Bing and Yahoo, as general SEO work for Google should also effect other search engines.  The first thing you should do is make sure that your site has been submitted to both and they have the location of your sitemap and robots.