I am Debra and am married to one of the descendents of Leopold Schuck. My husband, Andre Ahchak is the grandson of Agnes Mimi Schuck (who married Abel Ahchak from Sabah- then Borneo).
A couple of years back, relatives from Philipines and Germany got together in Singapore to put right the family tree. You are right, there is a book on this. The family is apparently also doing a book on the history of the Schucks. I am very bad at remembering names, but if I am not wrong, we still have relatives staying in Zamoanga (hope I spelt it right).
If you could get hold of this, please let me know too. There is also apparently a website on the family also.
Hopeto hear from you soon.
You could contact me directly at my email : firstname.lastname@example.org