Hi - I have some additional data for you concerning this Richard Willis Jr. who mar. Nancy Wier. They are ancestors of mine, and I have been finding bits and pieces of info on them recently. It may require some adjustments to your existing data - you can decide. All the data below requires verification.
First, Richard Willis apparently died 19 Jul 1813, and his will was probated Sep 1813 in Spartanburg Co. SC (I know it's district, but I am using county in all my records just to simplify things). I have seen death dates of 1836, 1826, and 16 Nov 1816 for him, but if the probate was Sep 1813, then he certainly died before then. I haven't seen the probate records myself. Some of the data concerning guardianship of his 3 daughters is in Pittsylvania Co. VA records, as that's where his wife was from, and her brother Armistead Grief Wier was their guardian, at least for some of the time before they married. After Richard died, I lose track of his wife - maybe she moved back to Pittsylvania Co. VA after her husband died, maybe remarried. I have seen the year of their marriage as 1807 instead of 1806, so am not sure which is correct - the orig. record should be consulted to break the tie.
I have Richard Willis Jr. as the son of Richard Willis Sr. (1746-1837) and Drucilla Pearson Barnett (1755-1845) of Spartanburg Co. SC. There is much on them in various places. The disagreements over the death date of Richard Jr. may have resulted from confusing him with other of the same name, including his father.
Richard's wife Nancy Wier was the son of John Wier b. 12 Jun 1754 Cumberland Co. NC, d. 22 Jun 1839 Pittsylvania Co. VA, and Sarah Burton b. 27 Apr 1762 Louisa Co. VA, d. 6 May 1836 Pittsylvania Co. VA, mar. 7 Apr 1778. You probably already had this data.
Richard's daughter Sarah - she was b. 11 Mar 1810, the date from the Bible of her 2nd husband Joseph Allen. However, her tombstone says d. 7 Oct 1888 age 78y 7m 28d, so b. 7 Feb 1810. I'm using the Bible date, which is more likely to be correct. This Bible also says that Sarah had a son Robert Baxter b. 10 Dec 1827, but doesn't name her first husband. I think it might be John Baxter, as there is a marriage Sarah Willis to John Baxter 13 Feb 1827 in Pittsylvania Co. VA. If this is the same couple, then John Baxter d. betw. Mar 1827 (when Robert was conceived - he may have been a posthumous child) and 9 Jan 1835 when Sarah (Willis) Baxter married Joseph Allen (this 1835 marriage date is also from the Bible; they were probably married in Spartanburg Co. SC, because they didn't move to Itawamba Co. MS until about 1843. Sarah had 7 ch. by Joseph Allen. Joseph and Sarah are buried in the Old Mackey's Creek Baptist Church cem. in Itawamba Co. MS; I have seen their tombstones.
Richard's daughter Martha was b. 1 Nov 1810 Pittsylvania Co. VA, perhaps in Danville, but the town may be someone's guess based on where the parents were married; maybe there are some land or tax records which would place them somewhere in late 1810 (about the time of the census). You will notice that Martha's birthdate conflicts with her sister's birthdate of 11 Mar 1810, which tells me that either Sarah was actually born on 7 Feb 1810, or the birthdate of Martha or Sarah is wrong altogether. Martha mar. bef 1831 James Madison Sutherlin (Southerlin/Southerland/etc.), probably in Pittsylvania Co. VA, and had 10 children b. in VA, SC, and MS; Sutherlin had moved to SC by 1841; note a 15 Jan 1842 letter written by Joseph Allen of Spartanburg Co. SC states "My brother-in-law James M. Sutherlin has got this fur from Virginia and is awanting for me to sell and will stay till next fall for me." The Sutherlin family did move to MS before 1845 and are living in Tishomingo Co. MS in 1850 (1850 census Tish. Co. MS, northern div., no. 683: J. M. Southerland 43 (42?) VA, Martha 38 VA, Ann 19 VA, Francis 17 f VA, James 14 VA, Martha 13 VA, Emily 9 SC, Pochahontas 5 f MS, Mary 3 MS - note that Martha is 38 here, so b. 1811-1812, not 1810, but the age could be wrong). James Sutherlin apparently went on to TX (where many of his MS relatives also moved at various times between the end of the CW and 1900), and d. 3 Feb 1893 Blum, Hill Co. TX. Many Allen, Beachum, and Rogers relatives also moved to Hill Co. TX. James Sutherlin was b. 28 Jun 1809 Pittsylvania Co. VA, and these exact dates may suggest that his tombstone is still up and readable in TX - I haven't looked for a cemetery record, nor do I know where/when his wife Martha died and was buried.
Richard's 3rd daughter Lucinda - she was b. ca. 1812. She may be the same as the Lucinda Willis b. ca. 1813 Anderson dist. SC, d. Jan 1888 Smith Co. TX (also seen as b. 15 Jun 1814, d. 27 Jun 1882, bur. Swan, Smith Co. TX) who was mar. 15 Jul 1834 Anderson dist. SC to Aaron Stuart Smith (b. 5 Apr 1810 Laurens Co. SC, d. Jul 1861 Smith Co. TX, son of Samuel L. Smith and Mary Harlan), 9 ch. However, some sources may have this Lucinda as dau. of an Edward Willis - this Edward may be Edward H. (1794-1848), the brother of Richard Jr., which I would doubt because Edward H. lived in Spartanburg Co. SC, not VA where Martha was born, he had no dau. Lucinda that I know of, and his first ch. was born 1814 (or maybe there's a different Edward). I haven't looked for the Aaron Smith family in the 1850 census of MS, etc..
I would love to get data on Lucinda from someone who knows the details, and would also like to know when/where Martha (Willis) Sutherlin died.