My question is, will Endpoint be safe to use on a live production server?
If we are talking about GA version, then yes: installations on the windows servers OS’s starting from 2008R2 SP1 are supported. Several users have shared their results of backing up the DC in this thread: Endpoint Backup. Backup of the Domain Controller
The server functions as a domain controller and I am concerned if the backup runs at night and over-runs (into the production hours), will this affect the users accessing the server?
I believe, it depends on how the backup schedule is configured. For instance, you can set the daily schedule to start the backup every evening.
Does endpoint use a snapshot technology?
Yes it does.