I think your forgetting the reason Robert called off the hitman, it was because Chas had changed her mind about telling Chrissie about the affair. Had she not Robert would of been responsible for 2 deaths. Also eve if he didn't mean to kill Katie he still meant to hurt her and was pushing her around and making threats. One last thing, it isn't Ross' fault that Aaron was thick and picked up the gun and hid it in a shockingly bad place instead of just getting rid of it.