You know what...this IS actually a good discussion (at least for now).
The problem with saying evil is a thing of negation is verses like Isaiah 45:7 or even Lamentations 3:38 that declare that evil comes from God and is the creation of God.
I will go ahead and respond directly to your post unlike any response by you. These verses are being taken out of context by you. I am sure it is not your intention but it is true none the less.
To address the claim that Isaiah 45:7 isn't talking about evil, to say so ignores the meaning of the Hebrew רַע which means 'evil' and is translated plenty of times as 'evil'.
The ESV translates that word evil in that verse as calamity. Just because a particular word is translated one way in one or more verses does not mean it must always be translated that way each and every time. I addressed the issue of context in the op. It seems you did not read it. I would suggest you go to your pastor and have him help you understand how words are placed in different contexts in scripture. He may be willing to give you a basic understanding of these things.
Then there's the claim that only evil can create evil...which there's no scriptural proof of. If only evil can create evil, how did creatures that God created as good do evil? If they got it from Satan, how did Satan do evil? For God created Satan too.
Scripture does not tell us where evil originates. Scripture does not tell us that God made Satan evil. To suggest that is to speculate and form a view from silence rather than a clear declaration.
Speaking of רַע, the mere fact that God created a Tree of Knowledge of Good AND Evil proves the statements that evil is just a negation false for if it were, the tree would have been the Tree of Knowledge of Good...and the creation of such a tree would make the statement that God didn't create evil false.
This statement is question begging. One does not lead to the other.
So if you prefer to refer to evil as the absence of good, then the Tree of Knowledge of Good and Evil is in fact the Tree of Knowledge of Good and the Absence of Good and Isaiah 45:7 reads "God...creates the absence of good". How do you create an absence of something? Or even Lamentations 3:38 should read "Is it not from the mouth of the Most High that good and the absence of good come?" Maybe you all would advocate an ATV bible (Augustinian Theology Version).
The ESV translates that as good and bad not good and moral evil.
Then verses such as James 1:13 would sound like nonsense. "God cannot be tempted with the absence of good nor does He tempt anyone with the absence of good." ?!?!?
James 1:13 is in fact talking about a moral evil as that is the context. Since God cannot tempt us we understand that He does not author it.
The importance of believing that evil is an actual substance like good is and that God had something to do with the creation of it is that you know He can control it. How do you control something that doesn't exist but is only a negation of something that does?
Darkness is nothing more than a lack of light. You control darkness by adding light. Same with moral evil. You control it by adding moral good. I described just how God controlled it in the op.