I know that Jupiter has a bunch of trailing asteroids surrounding it dubbed "Trojans". Due to its massive gravitational pull Jupiter is likely a co-creator of Earth in many ways, diverting asteroids into its orbit long before the moon had a chance to try to catch them. However, we've since discovered a single Earth trojan as well, I'm wondering what the potential risk/benefit is of these Trojan Asteroids... The answers to that question say Earth trojans aren't very long lived, but what size class would a Trojan have to be to potentially disrupt life on earth? What's the maximum size class of an asteroid that could become a Trojan given our mass? I know some moons used to be asteroids, could a Trojan become a second moon and disrupt tidal events?
In addition to this, does the massive trojan field Jupiter has further protect earth from incoming bodies? If an incoming asteroid collided with the Jupiter Trojan field at the furthest point from Jupiter, would the asteroids be enough to stop it before it reached an inner orbit beyond Jupiter, or would they just slow it enough to be potentially dangerous?