You really have uncovered a LOT of info about this family before the 1850 Census. You can contact the Nelson County Clerk, www.nelsoncountyclerk.com/
for deeds/mortages, marriages and voter records.
You can contact the County Circuit Court Clerk, http://courts.ky.gov/courts/clerks/Pages/default.aspx
for will/probate records, divorce and guardianship records. I'm not sure who you would contact for old tax records but maybe one of these two other departments can help you with that. Successful Searching!