And
"Jefferson's plan for gradual emancipation included removing the freed slaves from the United States when they reached adulthood."
What am I supposed to show you that you already know?
The provided image is not related to the institution of slavery, it is only personal matters of Jefferson. Next.
"Your source states that it presents unreliable information...."
The Chicago Historical Society found no reason to discount the material, so the word unreliable is inappropriate.
The word you are grasping for is "unverified". Press CTRL+F, the word "unreliable" is not present.
The fact is, this isn't Dan Rather around here, nor is it historians who managed to agree to a DNA test when such DNA doesn't exist. Here's the thing, given that Jefferson never fought at any time on the side of preserving the institution of slavery, the pattern certainly matches.
We aren't talking about someone who openly argued for "slavery as a positive good" and all of a sudden here comes this Lemen documentation - this is without merit. It does not match the pattern.
The author of the Northwest Ordinances with its heavy abolitionism sending a guy to go preach abolitionism - entirely believable. Now, yes, the documentation is unverified. But you're alone to say unreliable.
You can't even point to a time when Jefferson called slavery a positive good and the guy spent what, 50 years in the public light legislating and negotiating and all sorts of it.
ProgressingAmerica: The Chicago Historical Society found no reason to discount the material, so the word unreliable is inappropriate.
There is a JSTOR article that directly addresses the papers of the Leman family referenced by MacNaul's 1915 paper: "A Mighty Contest'': The Jefferson-Lemen Compact Reevaluated — James. A Erdstrom, Journal of the Illinois State Historical Society (1998-), Vol. 97, No. 3 (Autumn, 2004), pp. 192-215 (24 pages)
Here are some choice quotes from the paper (bold and underline are emphasis mine):
"Given the significant, even radical, implications of the story of the Jefferson-Lemen Compact, it is difficult to understand why MacNaul made no thorough effort to verify the authenticity of the relevant documents. Even if those original materials had "gone the way of all paper" and were no longer available, it is hard to believe there would be no other documents to support the story - in the Thomas Jefferson papers, for example. As it was, MacNaul chose merely to present the Lemen family papers as published without inquiring too closely as to their provenance and without attempting to find any corroborating evidence in other archival collections. Indeed, in the years since MacNaul's publication, there has been no systematic effort to evaluate either the documents or the story they narrate."
"This much is clear about the Lemen family papers: there are a total of thirteen documents comprising the collection, and of these, eight are directly relevant to the story of the Jefferson-Lemen Compact. Of these eight, six are definitely fraudulent and the remaining two are skeptical."
The paper then goes on to describe in detail why the various papers are fraudulent by contradicting them with other publicly available letters and evidence. With regards to Jefferson, we have this section which seems relevant:
"The fifth document is a letter from Thomas Jefferson to Robert Lemen (brother of James Lemen Sr.) dated 10 September 1807. As earlier mentioned, John Mason Peck quotes only a fragment of this letter in his alleged history of the compact. In it, the third President wrote of his regard for James Lemen Sr. and asked Robert Lemen to urge his brother to visit Jefferson. There are several problems with the provenance of this document. Jefferson was a meticulous correspondent, carefully preserving the letters he received and copying those that he sent. There is no record of this letter in any of the sources consulted, and, for that matter, no reference to any correspondence or contact between Jefferson and James Lemen Sr. Jefferson wrote letters on 8 September and 19 September, but none on 10 September 1807. Jefferson was traveling between Monticello and Bedford, Virginia, during the period of 9-17 September, which would not have been conducive to maintaining his usual painstaking correspondence habits."
"The next document, the alleged diary of James Lemen Sr., is in many ways the most problematical of all the Lemen family papers. The author of this diary penned it in a very self-important, self-aware style, almost as if the author is consciously composing it for the audience of posterity. It moves erratically from brief references to Lemen's family to detailed descriptions of his political and religious activities, and overall it lacks the authentic voice found in pioneer letters such as those written by Gershom Flagg, who settled in Madison County in 1818. Moreover, there are clues within the diary that detract from its validity. For example, on 28 December 1785 Lemen recorded that Jefferson's confidential agent gave him one hundred dollars "of his funds to use for my family, if need be, and if not to go to good causes, and I will go to Illinois on his mission next Spring and take my wife and children." A careful examination of Jefferson's account book for the time period covering 2 May 1784, when Jefferson and Lemen supposedly met, through 31 December 1785 reveals no transaction corresponding with this incident."
"Ultimately, the central difficulty of establishing the validity of the story of the Jefferson-Lemen Compact lies in the complete lack of provenance for the Lemen family papers. No one, certainly not Joseph Lemen, who was more responsible than anyone for attempting to popularize the story, ever produced the original documents themselves or validated copies. There are several notations from James Lemen Jr. within the diary as published by Willard MacNaul: "I have examined the within notes and find them to be true copies of notes kept by Rev. James Lemen, Sr., which were fading out."59 In other words, he had undertaken the rigorous task of comparing transcriptions of the diary entries with the originals. However, these, too, are questionable due to the date of attestation: 4 June 1867. Lyman Copeland Draper, who corresponded with Lemen Jr. in the course of Draper's research on early Midwestern history, recorded that, during the summer of 1868 (only one year after the attestation date), he called upon Lemen Jr. and found that "his memory had all faded out, so he could give no information whatever." Moreover, in his correspondence with Draper a few years earlier, James Lemen Jr. made repeated references to his inability to provide substantial assistance to Draper's research owing to his own feeble health. In this context, it is questionable whether Lemen Jr. would have been capable of such extensive copy editing."
Even contemporary reactions to Macnaul's 1915 paper were clear as to the fact that such a compact relied upon the authenticity of the Lemen papers, and that the lack of being able to authenticate them was problematic. "Moreover, if the original papers were as valuable as Joseph Lemen suggested, there should be at least a record of them somewhere, even if the papers themselves have disappeared. By rights, some provision should have been made for their retention and preservation. The examination of the wills of both James Lemen Jr. and Joseph Lemen, written in 1870 and 1906, respectively, reveals no reference to the Lemen family papers."
Overall, despite the Lemen-Jefferson's position in popular history, "Scholars who have studied the life and career of Thomas Jefferson likewise call the story of the compact into serious question. Merrill D. Peterson wrote in 1960 that in spite of initial support from some historians, "the best authorities on the Old Northwest have for some time regarded it as false or unproven." He also noted that Julian Boyd, editor of the Jefferson papers, had found no record of any relationship between Lemen and the third President. Boyd himself commented directly upon the issue to author Lyn Allison Yeager in 1975 by saying "The so-called 'Jefferson-Lemen Compact' is without foundation ... that such a compact existed is inherently implausible and, with respect to Jefferson, wholly uncharacteristic."...Why Joseph Lemen chose to put forth questionable - indeed, fraudulent - documents in the service of a spurious story is at best a matter for speculation. As shown, Lemen was ardently anti-slavery and it seems unnecessary for Joseph Lemen to perpetuate a rumor linking James Lemen Sr. and Thomas Jefferson in a conspiracy to outlaw slavery in Illinois. The history of the Lemen family's service in the antislavery cause is documented and unimpeachable, and their legacy merits respect and admiration. In the face of the evidence and the doubtful validity of the Lemen family papers, however, the story of the Jefferson-Lemen Compact must ultimately be consigned to the realm of myth."
All told, in spite of the claims of the original post, I don't think this alleged compact is worth boasting about, at least insofar as it concerns Thomas Jefferson.