Norn Cohen, "Long Steel Rail," devotes a chapter to "Reuben's Train/Train 45/900 Miles," pp. 503-518, including words and partial score for Emry Arthur, "Reuben, Oh, Reuben," p. 503.
The only differences from your transcription are-
...he broke his fireman's neck
Reube is the spelling used.

Cohen quotes in full Riley Puckett's "Nine Hundred Miles from Home," with partial score.

Cohen remarks on the opening of Grayson and Whitter's Train 45, with the verse:
"Oh, you oughta been uptown, an' seen that train come down,
A-heard the whistle blow a hundred miles"
"When the verses are written in this fashion, each line ends on the tonic. Beside the tonic, the melody uses primarily the third, fourth and fifth degrees of the scale. In contrast, the "900 Miles" tune is twice as long. The first line is musically similar to "Reuben's Train" but the second line moves higher up the scale, to end on the dominant. The third and fourth lines are unlike "Reuben's Train."
At the end of the chapter, Cohen is uncertain whether, originally, there were two texts/tunes (contrasting Emry and Puckett as examples).

The first occurrence of the song(s) seems to be a fragment from two South Carolina Blacks, heard in 1905 by Robert Duncan Bass.

Cohen doesn't discuss the "Graveyard Blues" much beyond quoting a bit of Wade Mainer, "Old Ruben," 1941, which has the 'graveyard of my own' verse.

Perrow collected a verse in 1907 from East Tennessee whites-

3. WHEN I'M DEAD

When I'm dead, dead en' gone,
You ken hyer the train I'm on,
You ken hyer the whistle blow a thousand miles.
If I die a railroad man,
Jes' bury me in the san',
Where I ken hyer ole Six Hundred roll in the mornin'.
E. C. Perrow, Songs and Rhymes of the South, Jour. American Folklore, vol. 26, 1913.

FO' HUNDRED MILES FUM HOME
South Carolina, Negroes, MS of H. M. Bryan, 1909

The rain it rained, the wind it blew,
The hail it hailed, and the snow it snew;
And I wuz fo' hundred miles away fum home.
The tracks wuz filled with snow,
When I heard the station blow:
And I wuz fo' hundred miles away fum home.
We just crossed Deadman's Track
When No. 14 hit our back;
And I wuz ... etc.
(Unfortunately, this is all that is reported).
Perrow, same issue.