Passive bonus "increased damage equal to your percent health remaining"

Does Paladin passive “increased fire, lightning, physical damage equal to your percent health remaining” mean that at full health you have +100% damage?

It isn’t displayed in stats, right? I have below 100% fire and lightning damage.

Your interpretation is correct. Full health = 100% increase. Often times, boosts aren’t reflected clearly in stats or tooltip DPS. For instance, Fresh From the Forge and Patient Doom don’t increase tooltip damage for applicable skills when it is up.