The evidence supports it. The South produced between 73% and 84% of all European money, goods and services imported into the United States. US law (among others, the Navigation act of 1817) caused those imports to arrive in New York instead of the areas in the South where the trade goods were produced to pay for them.
As all of Washington DC's income came from taxing imports, 73-84% of that tax money depended upon those Southern exports. When the European trade shifted south to Norfolk, Charleston, Mobil and New Orleans, that 200 million dollars per year in 1860 trade value was going to move to those ports, and New York (and the Washington tax collectors in New York) were going to be deprived of that money.
For one thing, in the buildup to the Civil War, there was an animated national debate over whether any State even had the right to secede from the Union.
One would think that they could look "four score and seven years" into the past for the valid answer to that question.
Your other points are worthy of further reply, but I think these two points to which I responded deserve superior consideration to any other remaining points.
“US law (among others, the Navigation act of 1817) caused “those imports to arrive in New York instead of the areas in the South where the trade goods were produced to pay for them.”
the Navigation act of 1817 requires cargos shipped between American ports be carried on American flagged ships. If a cargo was to be shipped from Boston to New Orleans, it had to be carried by an American flagged ship. That was what the 1817 Navigation act required. A British flagged ship carrying cargo from Birmingham England to the U.S. was free to go to any port in the United States that the ship’s captain chose.
The reason why New York, Boston, or Philadelphia handled more ships is because they had the capacity of handle large numbers of ships. New York’s capacity equaled the combined capacities of Norfolk, Charleston, Mobile and New Orleans.
Boston’s capacity was not to far behind New York, and was greater than any of the Southern ports. Philadelphia could also berth more ships than any of the Southern ports.
Each day at anchor, waiting for a berth to off load costs the ships owner money.