"I am a staunch proponent for the blues starting right here at Dockery Plantation and the surrounding area." There is no credible evidence supporting that idea.

"Handy first heard the blues on the courthouse steps here in Cleveland" Nope, the most famous book connected with him, _Father Of The Blues_, said he heard the blues "Got No More Home Than A Dog" back in the 1890s, years before he found a particular job in Clarksdale and while living in Clarksdale heard Prince McCoy's band in Cleveland, MS (in about 1904). When Jack The Bear Wilson borrowed "Joe Turner"-family melody and chord progression for an 1898 piece of sheet music, e.g., that was also years before Handy heard McCoy's band (or the Tutwiler guitarist).

"[L]iterally hundreds of true authorities" can provide and have provided zero credible evidence that blues music started in the Yazoo-Mississippi Delta.

I agree with leeneia that the railroads have been underrated. They were often mentioned in early blues songs.

Boogie woogie is a style of playing non-blues material or blues material. So supposing the style was being used in the 1870s, that doesn't tell us anything about whether it was being used on blues material yet (apparently not).