1. Are you making (for simplicity) the assumption that the macro state of eq. has multiplicity of $N$?
2. You make the claim that for a thermodynamic system in eq, all the microstates belonging to the macrostate of eq. have the same probability. Does the type of system plays a role? Meaning, whether it's isolated, closed or open for your assumption to hold true? I know for a fact that that's the case for an isolated system. @ACuriousMind