You are wrong about what Jefferson said.
Thomas Jefferson, in his First Inaugural Address, said, “If there be any among us who would wish to dissolve this Union, or to change its republican form, let them stand undisturbed as monuments of the safety with which error of opinion may be tolerated where reason is left to combat it.” Fifteen years later, after the New England Federalists attempted to secede, Jefferson said, “If any state in the Union will declare that it prefers separation…to a continuance in the union…I have no hesitation in saying, ‘Let us separate.’”
At Virginia’s ratification convention, the delegates said, “The powers granted under the Constitution being derived from the People of the United States may be resumed by them whensoever the same shall be perverted to their injury or oppression.”
In Federalist Paper 39, James Madison, the father of the Constitution, clarified what “the people” meant when he said that the proposed Constitution would be subject to ratification by the people, “not as individuals composing one entire nation, but as composing the distinct and independent States to which they respectively belong.” In a word, states were sovereign; the federal government was a creation, an agent, a servant of the states.
On the eve of the war, even unionist politicians saw secession as the right of states. Maryland Representative Jacob M. Kunkel said, “Any attempt to preserve the Union between the States of this Confederacy by force would be impractical, and destructive of republican liberty.” Just about every major Northern newspaper editorialized in favor of the South’s right to secede:
New York Tribune (February 5, 1860): “If tyranny and despotism justified the Revolution of 1776, then we do not see why it would not justify the secession of Five Millions of Southrons from the Federal Union in 1861.”
What Jefferson said was, "The alternatives between which we are to choose [are fairly stated]: 1, licentious commerce and gambling speculations for a few, with eternal war for the many; or, 2, restricted commerce, peace and steady occupations for all. If any State in the Union will declare that it prefers separation with the first alternative to a continuance in union without it, I have no hesitation in saying 'let us separate.' I would rather the States should withdraw which are for unlimited commerce and war, and confederate with those alone which are for peace and agriculture. I know that every nation in Europe would join in sincere amity with the latter and hold the former at arm's length by jealousies, prohibitions, restrictions, vexations and war."
So are you suggesting that the south stood for unlimited commerce and war? And even at that, Jefferson is clearly talking about separation with the agreement of both parties, not unilateral separation by one.
In Federalist Paper 39, James Madison, the father of the Constitution...
While Madison may not have viewed the Constitution and a permanent agreement, without possibility of withdrawl, he is on record as opposing the kind of unilateral secession as practiced by the southern states. Secession should be with the agreement of both sides, not just one. As he pointed out, the idea that a state could secede at will is as ridiculous as the idea that a state could be turned out of the Union against its will.