- Hope I answered the tools part here: Standardize Quick Tools?
- Manage different user IDs via the admin enterprise dashboard (won't help you with the stamp issue)
- Custom stamps are per user. When a user creates and saves a custom stamp, the will always see their stamps when logging on. Stamps are stored here: C:\Users\<name>\AppData\Roaming\Adobe\Acrobat\2015\Stamps. I am probably missing something because I think it works they way you want it to work.
hth,
Ben