Get it straight.
Second, I will not read the rest until you correct a glaring error that I see so far has you off a wrong tangent.
Section 3402 is in Subtitle C - Employment Taxes.
But you are speaking as if it is operating on Subtitle A - Income Taxes.
Yes, 3402 DOES require the witholding of "an" income tax on employees.
But this is NOT the same income tax as imposed on all individuals with taxable income in section 1 located in Subtitle A.
You can't mix sections from subtitles.
You are generally on the right track, but took the "wrong turn at Albuquerque."
Get back on the right path, or else you are dooming yourself and those who follow you to legal and financial trouble.
It seems your material IS good for Subtitle C taxes, but you seem to have been sidetracked from Subtitle A taxes.
You'll need to cover BOTH if you want your OP title to stand up to scrutiny.