Can you use Swornbreaker more than once?

You'll have to make a choice.
Not only will each of the NPCs keep the Swornbreaker if you decide to help them, the weapon will also crumble to dust if you use it to free yourself of the Covenant. There's no way to help every person who regrets their pact, unfortunately.

You can also sell a broken Swornbreaker to Fletcher Corbin Day prior to going to Arx and it will be repaired on arrival.

Well, it's possible if you have no problem with taking advantage of some glitches.

I was on PS4, by initiating the conversation with NPC and then drop the sword on the ground before they take it. You will be able to gain an extra use.