Armstrong/Clark Connection

As posted on April 8, 2005, and after a more careful study of the 1850 U.S. Population census, Mahoning County, Goshen Twp; wherein James Potter Armstrong is found living with his wife and six children and others, a John Armstrong also is noted on Pg 562 of the same Census record as shown below:
John Armstrong age 45 farmer Ohio
Pheby A. age 39 New York
Louisa age 17 Ohio
William age 8 Ohio
Clark age 6 Ohio
Sarah A. age 4 Ohio
Mary I. age 2 Ohio
All are born in Ohio except wife, Pheby.

The most interesting person in this family is Clark Armstrong. He has been given the name “Clark” which is a little unusual for an Armstrong given name. As noted in the Blog of April 4, 2005, William Armstrong, the first born son of James Potter Armstrong, files a marriage application to marry Elizabeth M. Clark in 1854, about 10 years after Clark Armstrong is born. Furthermore, Clark Armstrong is found living with William Clark (father of Elizabeth M. Clark) family in the 1860 Census, Mahoning County, Smith Twp. Ohio.
A search of the 1860 Ohio Census for a John Armstrong with a wife Pheby results in nil. He is not to be found. On the other hand, Clark Armstrong, age 24, is found in the 1870 Ohio Census, Mahoning County, Smith Twp. He is apparently married to a Julia M., age 27; no children. In the 1880 Ohio census, Mahoning County, Clark Armstrong is found, age 36, with his wife Julia, age 39, and a son, William, age 9. William is probably their first born son and therefore, their marriage probably occurred about 1869.

Questions:
1. Is John Armstrong, noted above, the brother of James Potter Armstrong?
2. Is the wife of William Clark, Mary A. (born abt 1811), an Armstrong? Perhaps a sister of James and John? (If this is true,, Clark Armstrong left home at an early age to live with his Aunt and Uncle, William and Mary Clark)
3. What are the circumstances in the John Armstrong home that would cause Clark Armstrong to leave and live with the Clark family?

Research Needed:
1.Guardianship records in Mahoning County, 1850 – 1860
2.Wills and Probate records for Mahoning County, 1850 – 1870
3. Track William Armstrong, son of John Armstrong, and search for his records. RHB