Hi,
Thank you for the details, it helps us a lot.
I logged in to check your configruation, it was almost perfect. For your needs I changed the relevance options, so the taxonomy terms relevance is much higher than the description relevance: https://i.imgur.com/lqpRJ66.png
The exact matching was also enabled, so I turned it off, because otherwise the index table will not work: https://i.imgur.com/hI2gOpT.png
Now you should see much more results matching the product brands, as the descriptions.
