Hi,
Thank you very much for the details, it helps a lot!
So, I logged in and checked your configuration, and changed a few things, which I think will match your case the best.
While the plugin is very powerful, and tries the best possible ways to give the expected results – it is still only relies on pure mathematical calculations. That means, some results will probably seem less relevant by human intuition, but mathematically will be actually more relevant.
To get the best of the plugin for your case, first I changed the keyword logics as following: https://i.imgur.com/zgW5BXy.png
This will be a more strict rule for searches, as you have more than enough keywords (over 1.9 million). The single character keywords are no also accepted.
Then I adjusted the relevance for the titles much stronger: https://i.imgur.com/8a3ywTY.png
This helps balancing out the hunge amount of keywords in the content, which are much less relevant as the short titles.
Now a few searches seem to give me much different results, but I believe they are more relevant as well.
Ex 1.: https://i.imgur.com/iSuRoiV.png
Ex 2.: https://i.imgur.com/jsZJAIB.png
