8 Books Found

Based on your description:

"A boy and his mother go to live on an isolated farm with his uncle. They experience mysterious acts of sabotage by a sniper. The book is set in the Midwest. The main character is a young boy. His mother and uncle get married at the end of the book. The book was written prior to 1980. It is a mystery. There are acts of mysterious sabotage on the farm, and the boy has to figure out who’s responsible."