Then He must, "by necessity," be pure evil as well? According to you, He is just pure -- everything, the good and the bad. And according to you, the Almighty God is defined and limited by "necessity." That's not Christianity.
God's attributes are perfect in their balance, since God is perfect. You can't have love without anger, you can't have grace without wrath.
He is the author of all emotion and actions, and only He has that perfect balance, because, well, He's the only one who is perfect.
No, what we call "evil" is not in God's nature so He is not also pure evil. I did not say that God was everything, I said that God is what the Bible says He is. Evil and wrath are not the same thing. When God does wrath he does it for a righteous purpose, making it good. If God did evil himself he would be acting against His own nature, an impossibility.
In fact, it was you who limited God to love. The only way I used "necessity" was to show that God must be greater than your limit.
I believe, Luther himself shied away from the necessary conclusion that denial of free will leads to predestination of the reprobates as wll as the elect, and hence to God as author of evil as well as the good. Others did that step for Luther, most notably Calvin and Zwingli.
I don't think it bears more than a purely historical interest, who of the leaders of the reformed communities thought what. If you drop your computer from the window, it will stop working. What part of the computer broke in what order following the impact is a quandary for the curious mind, but that knowledge is not going to fix the computer.