Hi Mark, really good questions.
- How many links would Google count as part of the link juice model?
There are a lot of opinions about this subject and there is no clear answer (it's really hard to test). Some time ago Google removed the effect of "nofollow" attribute for internal links, to cut the advantage SEO's gained by "pagerank sculpting". I think they did this so that search engine optimizers don't have a big advantage over standard websites. My personal opinion is that in terms of link juice lost Google would count 5, but the page benefiting won't get double the value. I think Google would only count the advantages of one of those links, whichever the best (probably the one in content. But on the other side, the link juice lost is not so important. The rest of the pages won't necessarily rank for popular terms.
I think that in-content links get way more advantages than just the "juice" and anchor text. The neighboring text is also important, the fact that it's in a block of text it's also important. Also it brings value to the users, who, might want to see all the shoes models when reading about them. I think you should definitely use this approach but just make sure you don't take it to an extreme.
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20% to each link, but the shoes page won't get 20x2 from those 2 duplicate, maybe it will get 25 + some other advantages (personal oppinion!)
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Changing anchor text had some effect in the past, but recently anchor text has less and less importance. It probably still has value. It's still an important ranking factor for 2013, and I would use it if I was you. But I would bring it to a new level. I would also think about the words in the context of the link. Try to link from all the relevant sections of the websites, and as you point to the shoes page from different contexts, naturally, the anchor text will change. For example you could link through our "shoe collection" from an article which compares between your shoes and competitor shoes.
I wrote an article for YouMoz a few years ago, some concepts might be a bit outdated because the ranking factors changed a lot since then. However it might give you some ideas to explore from a new perspective -> An Intelligent Way to Plan Your Internal Linking Structure