You speak in terms of religious fervor about a matter that was simply normal activity. If you are writing "to serve", you seem to think of whatever it is you are serving with the zeal of a fanatic -- and it appears you think of all those who merely think differently than you as false prophets, benighted heathen, and idolaters.
Historical truth does exist. It is clear that Southern leaders put less and less effort into support for a "southern route" as the 1850s wore on. While it is certain that around 1853 there was strong support for some type of "southern route", the southerners themselves could not unite around one plan; their own division was their biggest problem. After 1854, Southern political support for that effort dwindled as "the South" concentrated on the slavery issue, on the Nebraska Act changes, "Popular Sovereignity" and pushing the expansion of slavery in "Bleeding Kansas".
From the article in the OP, the one you declared your familiarity with:
View attachment 313277
No one says the people of "the South" forgot about the Transcontinental RR. It simply was not an issue that was being pushed by "the South" because "the South" had other fish to fry. Very clearly, the politicians of "the South" chose to support Stephen Douglas and his RR plan when they wanted to get "Popular Sovereignty" written into the Nebraska Act; very clearly, their support for a "southern route" fell away after 1854. You cannot wish these things away and make them vanish to enhance your vision of history. If you wish to be taken seriously, you must acknowledge them and show how the real people of "the South" made these choices is they were as fanataic about this Transcontinental RR as you would have us believe they were.