Links below provide crash places of Halifaxes on 13 Aug 1944 according German reports.
Perhaps with comparison with info in Chorley's books and/or a look on the map what town is nr (a) Hamm, you may narrow down your search. Since the target was Rüsselsheim nr Wiesbaden, we can exclude the largest Hamm, east of the Ruhr area?
See
https://catalog.archives.gov/id/91177051 https://catalog.archives.gov/id/91177053
Apparently no Halifax losses on 12 Aug 1944.
Leendert