Nordtvedt gives a good visualization of Z58+ Z60-, including Z59+ Z60-, here on his "Tree for I1 Z58+ Z60-."
What's unusual doesn't seem to be Z59+ Z60-, since that includes the AS3, AS10, AS13, and Sw clusters, along with assorted outliers. What's unusual is CTS8647+ Z60-. Nordtvedt lists only two families who have tested like that: Callewaert and Fueller, neither closely related to one another. Both are singleton outliers dating back some 3500 years! You're right that F3916 seems to be all that you have left to test... not enough people to compare against to find any more SNPs.