We're not going to agree, but I want to ensure that what I'm saying is perfectly understood.
Of course God cannot lie. He is incorruptible, and He cannot deny Himself. I'm not suggesting He can or will do anything corrupt. When corruption comes into contact with Him, it is either destroyed or made whole.
[Just to draw a contrast here: With man it is the opposite. No matter how good, holy and just a man is, he is not incorruptible. His communication with corruption corrupts his good manners.]
So far so good.
(All I'm trying to do here is draw a contrast between your thought and mine. You will disagree with me, and my point here is not to convince you, but just to clarify. I want the reader to understand what I'm saying about your thought.)
You say God is good, but your presupposition is that good is an abstract, self-existing standard by which we know that God is good.
I am saying that God is good and good is God. Just to illustrate the point, I'm posed an impossibility. If God would speak an untruth, then it would be good, because He did it.
So, when I read about God's acts in the Scriptures, and they appear to go against that which to my mind is just and good, I don't interpret them to conform to my notions of justice (which is what noncalvinists do with passages like Romans 9), I accept them and understand that God is God. There is no other, and His ways are so much higher than mine.