Heya,
I think I've met a few of the people on that Amazon team (though I didn't see any authors listed on their report). I've studied LCA and have written a journal article on EIO LCA techniques, so hit me up if you have any questions on this.
I confess I haven't read through all of your website or all of the Amazon report so correct me if I'm wrong. It sounds like you're applying their singular carbon footprint value (I think I spotted ~200 grams CO2/USD) to any product's price on Amazon.
While this number should capture the entire upstream supply chain (including production, base materials sourcing, transportation, warehousing), it's imprecise to be applied in this manner. You can imagine some bulk good (say, metal tubing: https://www.amazon.com/Unpolished-1008-1010-Diameter-Thickness-0-8700/dp/B003TPJFJK ) might be really cheap (here, $16). Compare that to jewelry (Here's a nice ring for $13k: https://www.amazon.com/Diamond-Engagement-Roy-Rose-Jewelry/dp/B07GJZJ6DQ/ ). Your plugin would wrongly point out that a ton of steel tubing will have drastically lower emissions than a small piece of metal with some jewels attached to it. The tubing ought to have a much larger impact than the ring.
While that emissions value will be accurate, it's not precise.
To increase the precision, you'd have to apply sectoral level LCA values from each broad Amazon category. Can you pull the 1st level categories of products from a webpage? (Eg. electronics, auto parts, books, appliances, etc.) If so, it'd be fairly easy to translate those to specific industries in an EIO-LCA model (e.g. electronic manufacturing, auto part manufacturing, etc.)
It looks like Amazon uses the USEEIO model - that one came out in 2016-2017 and was sponsored by the EPA. It's legit and has a lot of good data in it. Check out:
https://github.com/USEPA/USEEIO
https://public.tableau.com/profile/john.sherwood#!/vizhome/USEEIOAnalysis/Dashboard1
PM me if you want to talk more outside of this thread.