You wrote - "Can anyone find Adam on the 1881 census?"There is NO 1881 census.
You also wrote - " Sometimes his name was spelled as Johnson/Johnsen rather than Johnston."WHAT are these records???
How do you know Adam was in Akron in 1887??? What is your source ??????????????????
1880 - Name: Gertrude Johnson Age: 9 Birth Year: abt 1871 Birthplace: Ohio Home in 1880: Franklin, Venango, Pennsylvania Race: White Gender: Female Relation to Head of House: Niece Marital Status: Single Father's Birthplace: Canada Mother's Birthplace: Ohio Occupation:
Groves Meltigum 41, OH Nancy C. Meltigum 40, NY Jennie Cuffield 18, OH - niece Gertrude Johnson 9, OH - niece
OH Marriage record - Name: Adam Groves Johnsen Birth Date: Birthplace: Age: Spouse's Name: Sarah Millekin