” By getting rid of the requirements of the Navigation act of 1817, and the high tariffs, the South would see a net gain of about 120 million dollars a year if everything else remained the same.”
But everything else did not remain the same. The British decided to buy their cotton from Egypt, to help them repay their debt for the Suez Canal project, and to keep out of a fight between those barbarous yanks. They sold the CSA some ramming boats and other hardware, and that was it.
Only happened because Union ships interdicted the market. In other words, as a consequence of the Union effort to control the South. Without the market disrupted deliberately by Union ships, those growers in Egypt and India would have never been able to compete with the Southern production. You can't beat free labor with paid labor. It ain't happening.
So again, to make sure we are clear on the underlying premise, the South would have acquired massive capital infusions from European trade *IF* the North had simply left them alone. Clearly the North did not do this, so the capital did not come, and foreign competition was allowed to get on it's feet when it would have otherwise been unable to do so.
You've got to keep your premises straight. You want to take the economic reality of what did happen and argue that this is what would have happened in an alternative timeline in which the South was allowed to go it's own way in peace.
The economic disaster for the powerful men in the North did not occur precisely because they used their influence with the government to launch a war against the South to stop it from happening.
Think Logically. Think clearly. Be objective.