How do I know what power spring I'd need to get? Or would I need to try several?

So you mean your Black Diamond doesn't use those parts at all or you don't have them?

Do I need the nipple protector thing? I figured out what the other small handle return spring does. I don't need it it just doesn't automatically push the little handle forward again after I pull it back to **** it. It stays back unless I push it forward manually.