Can ad_form be used with tables where the primary key spans more than one column (a compound key)? A number of parameters such as -select_query and -edit_request seem to only work when the built-in key management feature is used.
I find that the more complicated the things I try to do with ad_form, though, the more I feel like I'm cludging around to make it work.
In this case, the solution I've used is to use a sequence not related to your table, like acs_objects_seq (or something like that). That should give you double-click protection (I believe), but free you from the constraints of using a single column key.