I have the information regarding the marriage of Margaret PARKER and John G. WOOD from three sources - family record, John's obituary, and the Illinois online marriage database. I am hoping to find Margaret's obituary soon. Also from family record, Margaret's mother remarried to a Thor Fell (possibly Thomas) while Margaret was young. I have found no sources to support that claim, however.
As far as the 1860 census, John and Margaret are found in Brookfield (Crotty post office), LaSalle, Illinois, with three children (all listed in the family record).