Yes, there was a period when footers were getting extremely large (and link laden) in order to try and drive as much link strength as possible to internal pages, and this was spread out through out the site. Here's a blog post from a couple of years ago that looks into it even more thoroughly: http://moz.com/blog/internal-linking-strategies-for-2012-and-beyond. But both Moz and Zappos have thinned down their footer links though from even this example. Rand also goes into general home page design (and why people have moved away from keyword stuffing on it) here: http://moz.com/blog/what-should-i-put-on-the-homepage-whiteboard-friday, which also helps get to footer links in a round about way.  Cheers!

My guess is that it's less of a technical constraint and more of a non-match for Google News guidelines.  There are several things in there that could trigger the boot, (https://support.google.com/news/publisher/answer/40787) such as:

Stick to the news--we mean it! Google News is not a marketing service. We don't want to send users to sites created primarily for promoting a product or organization, or to sites that engage in commerce journalism. If your site mixes news content with other types of content, especially paid advertorials or promotional content, we strongly recommend that you separate non-news types of content. Otherwise, if we find non-news content mixed with news content, we may exclude your entire publication from Google News.

Journalistic standards. Original reporting and honest attribution are longstanding journalistic values. If your site publishes aggregated content, you will need to separate it from your original work, or restrict our access to those aggregated articles via your robots.txt file.

News content. Sites included in Google News should offer timely reporting on matters that are important or interesting to our audience. We generally do not include how-to articles, advice columns, job postings, or strictly informational content such as weather forecasts and stock data.

And so on... If you think you're in the clear try going to the Google News specific help center (on the previously linked page) and submit your site for inclusion.

I think this partially depends on resources you'll be able to expend on one vs two sites as gains made on one would have to be repeated in some way with the other site. Dev work on a single domain with dual pricing could be a bit more complicated than two separate domains with one singular price and fulfillment system.

Do you have any data on what customers of yours might prefer? I.e, would having the '.ca' help push conversions?

If the marketing plan is very much content marketing focused, you'll probably be better served by a single domain, but that could change depending on how regionally focused the sites are.

Mostly no on iFrames, or not in a reliable way. Redirect 303 is more uncommon, but similar to a 302. Either one is not the way to permanently send old content to new. Google has a guide on redirection here: https://support.google.com/webmasters/answer/93633, and iFrames here: https://support.google.com/webmasters/answer/34445.  Cheers!

I'd choose one of the top 3 options listed as subdirectories are going to better associated with the root domain than subdomains.  Moz has done several tests of this with one of their latest recaps here: http://moz.com/blog/subdomains-vs-subfolders-rel-canonical-vs-301-how-to-structure-links-optimally-for-seo-whiteboard-friday. From Rand's WBF:

You're asking, "Should I put my content on a subdomain, or should I put it in a subfolder?" Subdomains can be kind of interesting sometimes because there's a lot less technical hurdles a lot of the time. You don't need to get your engineering staff or development staff involved in putting those on there. From a technical operations perspective, some things might be easier, but from an SEO perspective this can be very dangerous. I'll show you what I mean.

So let's say you've got blog.yoursite.com or you've got www.yoursite.com/blog. Now engines may indeed consider content that's on this separate subdomain to be the same as the content that's on here, and so all of the links, all of the user and usage data signals, all of the ranking signals as an entirety that point here may benefit this site as well as benefiting this subdomain. The keyword there is "may."

Cheers!

Here's a discussion on it in the context of YouTube's TOS: https://productforums.google.com/forum/#!topic/youtube/qN8MrLI4mHM.  I'd consider it a blackhat social tactic, and one to avoid for the long term health of a business.

Hi Angelos. Dofollowing internal links, is fine, especially in the context of relevant articles as those links are tying together information both in relation to search and for users that want to quickly dig deeper while reading your work.

Mostly no.  I say 'mostly' because a lot of times when you look at a site using www and no-www if both of those work they're almost always pulling files from the same location (hence the warnings around duplicate content), so both www.domain.com/robots.txt and domain.com/robots.txt are going to work.  This is the dominant example of a subdomain sharing a robots.txt file. However, on domains that are set up as their own subdomains they have different robots.txt.  Take a look at the many differences between subdomain1-1000.wordpress.com/robots.txt vs wordpress.com/robots.txt.  If you set up a subdomain that isn't just a reflection of your root domain, then you'll need to create a robots.txt file as well. Cheers!

Hi Andrew. Yes, Google has been known to pull other text for its results instead of what is in the meta description. Same goes for title tags as well. Like you've inferred, what they're trying to do is match their search result with the most applicable portion of text from what they deem the most relevant page.

Edit. See: https://support.google.com/webmasters/answer/35624 for Google's larger explanation of this process.  Cheers!