Go to The Militia Act of 1792. That document defines the state Militia. In detail.
"No free man shall ever be debarred the use of arms." - Thomas Jefferson is quite clear in its meaning. Note that it says Free Man and not Freeman.'
Yes, because you quoted it incorrectly. The correct quote is, "No freeman shall be debarred the use of arms within his own lands or tenements."
Jefferson was not talking about the second amendment. He was proposing that language for the 1776 Virginia State Constitution, 12 years before the second amendment was written. It was rejected by the Virginia State legislature.
"Every other quote by Constitutional authors, contributors and supporters says effectively the same thing."
I know. But, like Jefferson, they're not referring to a right protected by the second amendment.
"I'm sure that the founding fathers would have no problem with resident aliens being armed."
I'm sure the Founding Fathers would say that it's up to the state in which the resident alien lives. In 1792, the second amendment, however, did not protect the RKBA of non-citizens. It still doesn't.