Indeed that marriage record must refer to Levi, no doubt misread in the transcription for "Lew."The death record of Aaron Tombaugh, in Ashland County, Ohio (1 May 1918) gives his birth date as 22 August 1848, supposedly in Branch County, Michigan (which is almost certainly erroneous), and says that his father was Levi Tombaugh, and that his mother was Margret Smith.
The same information is provided in the record of Aaron's second marriage, to Ida A. Honkus 3 Jan 1890, in Coldwater, Branch County, Mich.It says that he was the son of Levi and Margaret (Smith) Tombaugh, and that Ida was the daughter of Samuel and Matilda (Smith) Honkus.This is a little confusing as Aaron's first wife was also named Ida, and according to the 1870 census of Richland Twp., Miami County, they had a daughter named Matilda.
I was excited about the prospect that Levi Tombaugh's wife's maiden name was Strayer, but now it appears that that was her second married name instead.
Evidently Margaret must have died before 1870, as Adam is shown on that census as married to "Alena," age 46, born in Wurtemburg.Adam's youngest son, Charles, appears on that census as 8 years old.He is clearly Margaret's son, and not Lena's, as on the 1880 census it shows that his mother was born in Ohio, not Wurtemburg.
I am not clear about the connection to Hancock County, Ohio, other than the fact that as you say there were Tombaugh relatives there (and hardly anywhere else other than the homeplace in Washington County).