Question 1. Is the converse of Proposition $3.5.4 (c)$ of Bruns_Herzog true?
I can see that $R$ is cohen-macaulay. so if one can prove that $r(R)=1$ , $R$ will be Gorenstein.
Question 2. What about replacing "$H^i_m(R)=E(k)$" by "$H^i_m(R)$ is injective"?
Q1, Q2: Yes, this works even more generally:
This follows from Theorem 2.5 of http://arxiv.org/pdf/1204.2394v5.pdf by taking $M=R$ and $a=m$.