Divine Command Theory

I believe Dr. Gordon H. Clark affirmed the traditional divine command theory of ethics as the solution to the problem of evil qua ex lex. 

The traditional divine command theory is demonstratively false. 

(1) If the traditional divine command theory of ethics is true then moral values/duties are grounded alone in God's will. 

(2) Moral values/duties are not grounded alone in God's will.

(3) Therefore, the traditional divine command theory of ethics is false. 

Assuming (1) entails:

(4) God can legislate any action or act to be morally blameworthy or praiseworthy.  [Hence volunteerism]

Further, if we affirm (4), with possible world semantics, we are left with an implausible conclusion:

(5) There is a possible world which God legislates adultery to be praiseworthy in all possible worlds.   

(6) The actual world is a possible world. 

(7) Hence, God legislates adultery to be praiseworthy in the actual world. 

The only way out of the volunteerism from the traditional divine command theory is the tertium quid, the modified divine command theory, but it costs a philosophical price, it requires one must reject a robust doctrine of divine simplicity (i.e. The primacy of God's will: God wills His essence and His essence is His will; hence God's will and essence are one in the same qua divine simplicity).