Simplicity and necessity

Recently I asked some Reformed Thomists a couple of questions:

I've read a number of sympathetic expositions of the Thomistic understanding of divine simplicity, which I'll dub Thomistic simplicity for short. I've also read some criticisms. I have a couple of interpretive questions for the group:

One interpretation goes something like this: on a classical understanding, God's attributes are essential to his being. "Essential" in the sense that God cannot be other than he is. If God is omniscient, he cannot be other than omniscient. Same with the other attributes.

But if the divine attributes are mutually identical, then that generates a necessitarian scheme in which there are no contingent facts. If Thomistic simplicity is true, then whatever God wills, he wills essentially. If he wills the world to be, then he cannot will otherwise. If he willed to elect Peter and reprobate Judas, then it's not possible for Peter to have been other than elect or Judas to be other than reprobate. Thomistic simplicity collapses the distinction between actual and possible, contingent and necessary. God's choices/volitions are as essential to his being as his aseity, impassibility, omnipotence, &c.

Is that a correct interpretation of Thomistic simplicity? If not, where does the analysis go awry?

I received a couple of erudite but murky explanations, one of which appealed to mystery. 

Second interpretive question. According to Reformed theology, God's mercy and justice are not conterminous. Election and reprobation are distinct and divergent. Although God is never less than just in how he treats his rational creatures, God is often less than fully merciful or gracious (in the soteric sense) in how he treats some of his rational creatures. Roughly speaking, the elect receive divine mercy whereas the reprobate receive divine justice. Divine justice is essential whereas divine mercy is selective and discretionary.

Can Thomistic simplicity sustain that distinction?

I didn't receive any direct answer to that question.