"how to value organic traffic"

That's a different question than "how much can I get for a website?".

But getting to your real question of "how to value organic traffic".... that depends upon what you can do with the traffic (display adsense, sell merchandise, generate leads).

Although you can put a generalized number on that the bottom line for the buyer of your website depends upon how effective your website is at converting customers for a specific service provider.  The generic website that you have for sale has zero value for the service provider.

You are selling a sign post without a sign, not a money-making machine.

I think that you have a lot more money making potential selling SEO services than selling pre-ranked websites.

1) why would so many companies like Hubspot, others require email for content exchange if putting on site would do as well?

Here are two answers:

A) they want to spam you with email and sell your email to everyone on the planet;

B) the value of a sale is enormous, so they would rather have a sale than the ad clicks

Does the type of industry: B-B, vs B-C make a difference in how you would approach or is your answer blanket for all types B-B,B-C?

Publishing for everyone makes more sense for the B-C business because the number of potential visitors is enormous compared to the B-B.

If we go the route of publishing to site (not pdf)  does it make a difference whether a 12 page ebook is one long scrolling page or should the content be 'click to read more' which advances to another possibly optimized page?  If multiple pages then each page would likely be optimizing for pretty much the same content?

I put a few thousand words on a page but if you have more then I would break it into separate pages.  I would break the ebook into chapters or lessons each targeting a different keyword.

Has there been any correlation between top step (main menu) and 2, 3, 4 steps below the main navigation on relevance (with same content) in rankings?

Yes.  The deeper you bury the content in your navigation the deeper it will rank in the SERPs.   If you want to promote this for traffic, income, links, tweets, signups,  I would think that you would be showing it to every person who visits your website.  That's what I do when I have something hot, valuable and important.  If you fail to do that you lose the opportunity.

Just an opinion....

I would increase the number of items to something higher than 15.  Will increase the count that is shown by google and when I visit your site to shop I will not be frustrated by the need to page through categories.  Might conserve linkjuice and prevent a little keyword canibalization.

Gap is lucky to have such a short brand name.

In a lot of cases we are talking about egos that are enormous compared to the size of a brand as widely known as Macy's.

For my sites at least I think that the opportunity to grab extra sale through the title tag is more important than trying to communicate a weak brand when I am head-to-head with a Macy's.   I'd rather use my title tag to shout value propositions, elicit clicks and reach for more keywords.

When we are talking my brand vs Macy's I need to get my foot in the door with value and then impress them with service and quality.

I don't think that there is anything wrong with using the word "I" in these situations.  I believe that it is a matter of personal style.    I see it as more "transparent" than if the attorney used "The Law Firm of..." as that might convey to some people that there are multiple attorneys at the office and that my work might be given to associates.  It would make me feel that my work is going to be done by "The Man" or "The Woman" who is the face of the firm.

The only downside of this, is if the attorney does take on associates or partners in the future, then these articles would need to be edited for any service for which the work will be shared or for which the primary attorney will not be determining the philosophy and methods that will be used and holding signature authority over each job.

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Applying this to SEO...  If I hired someone to work on my websites and they were outsourcing that work to others, I would not be happy with that being done undisclosed.   If others are being used, I would want to know who is making changes to my site and be able to have full faith in their work, integrity and competence.   I realize that this is common practice by many individual SEO providers, just saying that I would not like it.

Should we nofollow these links in the secondary menu?

In my opinion, definitely not.  If you nofollow them then the pagerank that would have flowed into them will be lost.  If you keep these links on your site let the power flow into them.