Hi Scott,
basically you are mixing up address book entries and address-sets (groups).
Your command "delete security zones security-zone internet address-book address-set address Dave_home 70.x.x.x/32" tries to delete an address name 'Dave_home' within an address-set names 'address'.
The correct command should be:
delete security zones security-zone internet address-book address Dave_home
I hope this solves your issue.