In your conclusion you wrote:
The votes from bid-bots and paid voting services sum up to 28.7% of all votes by value for that day
But doesn't it sum up to 28.17+3.82+1.44=33.43%?
In general this is really a great investigation as it solves a long time outstanding question!
Thanks for your remark and cross-checking the numbers! A '1' got lost there: 28.7 -> 28.17.
The 28.17% are all votes directly from the bid-bots and paid voting services. On top of that are 3.82% + 1.44% from the vote sellers via smartsteem and minnowbooster.
In total 33.43% for bots + vote sellers for that specific day.