Google does limit the number of pages it crawls and indexes based on your PageRank. So if you don't have a lot of external links, then if you publish 10 articles a day they may not be crawled or indexed in a timely fashion. The higher the authority of your site, the more content Google will index, and sooner.

There are a bunch of sites that offer this service such as Alexa, Compete, Google Trends, etc. but none of them are close to accurate. But they can provide very rough ballpark figures as well as relative popularity:

http://moz.com/blog/testing-accuracy-visitor-data-alexa-compete-google-trends-quantcast

Another option, which is more time consuming but potentially more accurate, is to do some research on the site, and identify their top keywords. The Google Keyword Planner can help you with this, just pop in the URL and it will show you the keywords that the site is optimized for.

Then run the keywords through a rank checker and combine that data with estimated click through rates and the search volume for the keywords to estimate how much traffic they are getting. Multiply that number by 10 to account for long tail variations, and that will give you an estimate of their total traffic. Paid tools such as Linkdex can help with this.

For location pages, Facebook users can give the location a star rating on their page (if you visit the page, you should see it on the right hand column). Facebook will also prompt users to rate places they've visited in the right sidebar. I'm not aware of anywhere you can go to view the reviews, it just appears as a star review at the top of the page.

Google can easily identify navigational elements that appear on every page, and will ignore those for the purposes of identifying duplicate content. You don't need to be worried about your navigation being flagged as duplicate content, that's a standard feature of most websites.

That being said, you can be penalized for having lots of pages with little or no content (Panda). You'll want to make sure all the pages on your site provide some kind of actual value.

Yes, what you have is the proper format. The best way to submit sitemaps, of course, is to submit them via Google & Bing Webmaster Tools.

Sitemaps won't have much impact on your site unless you have a really large site, so I wouldn't focus on them too much. The best way to get content crawled & indexed by Google is good internal link structure and authoritative external links.

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/

BJS1976 makes some good suggestions.

Another option is to create a category type page that lists all the product variations on it, then canonical each of the individual products to the category page. That way, you still have multiple product pages, but as far as Google is concerned you only have 1 page with the content on it.

Directory links don't pass much link value, but it can still be useful to be listed in the top directories for local citations. Yext can automate the process if you're short on time & resources, but you can also submit to the directories manually for full control of the process.

They even provide a list of all the directories they submit to:

http://www.yext.com/blog/tag/business-directories/

As you yourself pointed out, there are perfectly legitimate reasons for owning multiple domains that all rank for the same term (ex: nike.com, nikeinc.com, nikeplus.com, etc). Not sure why you are arguing with what I wrote.

Where in Google's TOS does it say that ranking multiple domains for the same phrases is against the guidelines? My original answer is correct: Google will not penalize you for owning multiple domains, only if you are being spammy about it.

Google won't actively penalize you for owning multiple domains, unless you are going out of your way to be spammy about it. However, you will need a lot more resources in terms of link building, social media promotion, content production, etc.

In general, the best practice from an SEO perspective is to have a single site with the all the content living in subdirectories of the domain. Subdomains are considered in many cases to be separate sites, so you would run into the same issues as having multiple domains.

I would say in general links from within a post/article carry more weight than sidebar links. Sidebar links have been devalued quite a bit by Google, and with Penguin you could even potentially be penalized for a sidebar link on a site with thousands of pages. With that being said, I would not turn down a sidebar link from a high authority site if offered one.

PR can be deceptive because it hasn't been updated in nearly a year. So a site can still be high quality even if the toolbar PR shows a 0. It's always nice to get links from sites that are already ranking for your keyword, but make sure to do a thorough backlink analysis first to make sure they aren't spamming their way to the top. If the #1 result is using black hat tactics, it could take your site down with them when they inevitably get penalized down the line.