Reworking my site's link architecture

Hello all! I have an authority niche Wordpress website with ~50 pages. Using Amazon Affil to promote individual products. My main question is more of an overall one, "What's the best way to structure my pages?" Here's how it is now:

mykeyword.com (800 wds + recent posts)
- - /brand-name (400 wds + list of each brand's product page)
- - - - /product-page (250-300 wds)
- - /product-type (400 wds + list of each type of product)
- - - - /product-page (250-300 wds)

So if the page was myicechest.com, there would be myicechest.com/coleman for the brand page and myicechest.com/coleman/12-gallon-deluxe-143d/ (or whatever the product name is) for the product page.

However, here's my dilemma: Coleman and 12-Gallon are each Categories... I can't have both myicechest.com/coleman/ ... and myicechest.com/12-gallon/. See what I mean?

How do I structure it so I am getting the benefit from each of these keywords using Wordpress Categories?

And a bonus question: Above I listed the amount of personalized content I write for each 'section'. 800 for main page, 400 for sub sections, and ~300 for product review pages -- it is quality, researched content. Would this be sufficient to maintain domain authority?

Thanks so much!