Mary Fernald's marriage record to Lovett lists Lee, NH as the birthplace of her father Amos. Amos was born 1785. The only Fernald in the 1790 census of Lee, NH is an Amos Fernald with 2 males 16 and up, 1 male under 16 and 6 females. He seems to fit!
If Amos Fernald b. 1785 was born in Lee. It is likely that Amos of Lee in 1790 was his father. It appears that Amos Fernald "Sr." is in the Lee Census up to 1830. But I am unsure of his parentage as well!!!