Have found his death date - alas, to try to find his grave you'll need to head for Illinois, USA! Find A Grave shows he was buried 1900 at Braceville-Gardner Cemetery, Braceville, Grundy County, Illinois and Margaret and children are living there in 1900 Census (she already a widow).
Margaret and 3 of their children left Liverpool for New York on the 'Majestic' on 30/11/1892 - can only assume Jonathan had gone on ahead.
Annette