Yes, it looks correct. I think there should be a better way to get taxonomy (using WP native methods). Also, I see a bit strange names for custom post meta names (MPN Number and MPN2 Number) - please be sure they are stored in a database like this exactly.
You can check your hook using Sandbox / Test Index. Just put the product post ID into the input and press the button. It should show you all cluster values, including 'sku' and 'product taxonomy'. Next, you can go to Edit one product and press Update to force WPFTS to rebuild index for this product. After that, this product should become searchable by sku and taxonomy.
If so, you can press Rebuild Index to rebuild an index for all products.
You can upload images to the WP Media Library as well and add the image description to the image. WPFTS Pro can search these images by the description then.
Alternatively, you can create a special post type and upload images as "Featured Image" to each of these posts, and put the description and special information to the post_content or additional meta field(s) - depending on the number of data fields and type of information.
In both cases, WPFTS Pro will help you with the search.
Yes, the algorithm thinks the number of words here is more important than the exact phrase... Ideally, if we could justify the relative weight for the phrase matches. Currently, it's too low for your case, but I think if we can double it, this could solve the issue.
I think to put this parameter to settings in the near future. Thanks!
I just made a short check for Google Search results' appearance and I found that they are trying to extend the excerpt by other (not "good") sentences even there is only one "good" sentence and it's short (your case #1).
So yes, I think it would be a great idea to add one or two other sentences near the result to give more context information to the user.
At the same time, I know that some developers still want to keep excerpts as short as possible to keep more space on the screen for other results. So I think it will be a configurable option in WPFTS Settings.
Also, I would like to add a configurable option to put a text like "...other 5 appearances" at the end of the excerpt. Thanks for the idea!
We also have some other things to play with Smart Excerpts (for example, lots of developers asked me to add page numbers in case an excerpt was taken from the paged document), so I guess it will add those features one-by-one.
Also, the documentation for the plugin requires a sufficient upgrade, and I definitely will include this explanation there.