You have a point if the final destination of all those imports is New York. You do not have a point if it isn't.
That New York collects the tariff says nothing about who pays it in the end.
Craig does a particularly good job of showing how those same tariff laws, which supposedly were so beneficial to Northern industries, also protected Southerners’ production of things like cotton, tobacco and sugar from competition from overseas.
And who would have been competing with the South regarding Cotton and Tobacco? I know the Caribbean competed with them in Sugar, also using slave labor, but who could have competed with them in Cotton or Tobacco?
Being protected from competition that doesn't exist isn't being protected at all.
In 1860, Deep South and Upper South whites totaled about 20% of all US whites -- 5.5 million out of 28 million.
On average, those Southern whites were slightly better off than their northern cousins.
Of those 5.5 million, at most 3% (165,000) were wealthy plantation owners, and those folks were very wealthy indeed, certainly by standards of their time.
But there is just no possibility -- none, zero, nada -- that 165,000 very wealthy plantation owners accounted for any number remotely resembling 75% or even 50% of total US imports.
At best, those future Confederate states may have accounted for a disproportionate 25% of all US imports, meaning about half of those imports went through Southern ports, and half through northern ports like New York.