A. “You could’ve died.” There was a risk of dying, you were lucky to have survived! B. “You could’ve been dead.” Most unlikely and not good English. See Note 1. C. “You should’ve been dead.” Same as B. D. “You should’ve died.” There was very little chance of surviving.
Note 1. The two contractions, “could’ve” and “should’ve” do not fit well with “been”; because being