“Those who accept the Atonement are invulnerable. (T-14.III.10)”
Often we think that vulnerability is to be desired, that it makes us more loving people, more willing to share. But is there not fear in this? We don’t have to feel vulnerability to be loving. This quotation actually indicates just the opposite. We will, of course, be more loving to ourselves and others when we have accepted the Atonement for ourselves, and in this, Jesus says, we will be invulnerable. What a promise!
What does it mean to be invulnerable? It know that nothing can harm us. In the cosmology of ACIM, it says that we are living in an insane and illusory world in which the attacks of others do not harm us because they are not true. This sense of invulnerability will protect us from the slings and arrows that only seem to hurt us. In actuality, these slings and arrows do nothing.
MIRACLES EACH DAY 
I like your nuance on the Atonement. There is resurrection power which casts out all fear.