Question with using Isc -> Any errors?
\$V_{oc} = I_{sc} *R \$ 

Nope. 

\$V_{oc}\$ mean open-circuit voltage across A and B. i.e, when those terminals are open. Now you shorted A and B to find \$I_{sc}\$. 

Means, \$V_{oc}\$ = 0V now across A and B.