You've done a very good job of condensing it all down.
I think the following is Lazarus Smith in 1850 AL.
1850 United States Federal Census Lowndes Co, Alabama #150 Elazany? Smith 50 m planter $200?r SC Eliza Smith 45 f AL Susan Smith 18 f AL Julia A Smith 16 f AL Sarah Smith 14 f AL Lydia Smith 10 f AL Frederick Smith 8 m AL James Smith 6 m AL Richard Plawson? 16 m AL Samuel Plawson? 9 m AL George Plawson? 5 m AL Amanda Plawson? 3 f AL
There's a Susan age 30 from AL livng next door to L and Eliza Smith in 1860 Union Parish, LA. She was the wife ofRiley Agerton. She is possibly Riley's second wife. That could be the daughter Susan from the above census.