Product Catalog - fairly complex

I want to make sure I'm going down the right path on my structure.

Here's a basic outline of the products

Brand A

--GROUP A

-----Product Item(s)

--GROUP B

--GROUP C

--GROUP D

-----GROUP D-SUBGROUPA

--------Product Items(s)

Brand B

--GROUP A

-----Product Item(s)

---GROUP B

-----GROUP B-SUBGROUPA

---------Product Items(s)

So, I have a number of brands that have groups, some of those groups have subgroups... some do not. There are products that are available in both brands and need to be managed/edited in one location. All products will be contained in a group or sub group, though the depth of that grouping will vary (some will be 2nd tier others may be 3rd tier).

I'm structuring it the following way:

I have various collections that represent the major product groupings (level 1 - since I'll have nearly a hundred items, I'm thinking it best to use separate collections) I'm using Categories to indicate the brands the product is available in. I'm using Categories to indicate the sub-groups the product is available in.

I'm developing a page template for both Group listing view as well as a Detail view.

Question 1: Is this a reasonable approach. Any caveats I should be aware of.

Question 2: I'm concerned about navigation, as I need to generate the multi-tiered navigation dynamically yet still need to have the search results come up correctly. My initial approach is to create pages using my list template and parse the slug to search the categories to present the correct product listing - in this way I'm not generating the hierarchy automatically, but it seems more intuitive for my users, as long as they name things correctly.

Question 3: Simple question, methinks. I like how adding pages creates the main navigation, but there are cases where I need a link to another part of the site. How is this done. See rough outline below for structure details. Each Brand has a distinct look and feel.

SITE ROOT

-> Company Landing Page

-> -> Company Navigation

-> -> -> Brand A Products (I would link this to go directly to the destination target below)

-> -> -> Brand B Products

-> -> -> General company information

-> BRAND A

-> -> Brand A navigation

-> -> -> About the Brand

-> -> -> Brand A products menu {DESTINATION TARGET}

-> -> Brand A Navigation

-> BRAND B

-> -> Brand B navigation

-> -> -> About the Brand

-> -> -> Brand B products menu

-> -> Brand B Navigation

Sorry for being so verbiose - I'm new to Perch Runway, but am liking it quite a bit more than the other CMS systems I've used in the past.