No, it makes man the author sin. It's impossible for God to be the author of sin. It would be more possible for a square to be a circle than for God to be the author of sin. You are misreading(albeit purposefully now) what Calvin said. God works ALL things after the counsel of his will.
Was it God's will for Christ to die? Yep. There you go. Christ was unlawfully killed by the Jews. (murder is sin)
You err, this is proved by the fact that the Jews tried to kill Jesus at least twice before the appointed Passover day.
Jhn 8:59 Then took they up stones to cast at him: but Jesus hid himself, and went out of the temple, going through the midst of them, and so passed by.
Here, the Jew attempted to stone Jesus, but Jesus hid himself from them and escaped. God could not have caused this attempt to kill Jesus, as it was not the appointed time. Jesus had to die on the Passover.
Luk 4:28 And all they in the synagogue, when they heard these things, were filled with wrath,
29 And rose up, and thrust him out of the city, and led him unto the brow of the hill whereon their city was built,
that they might cast him down headlong.
30 But he passing through the midst of them went his way,
Here is another incident where the Jews attempted to cast Jesus off the brow of a hill to kill him, but Jesus escaped from them because it was not the appointed time.
These two incidents prove God did not cause or determine that the Jews would kill Jesus because it would have thwarted God's own plan that Jesus die on the Passover as a sacrifice for the sins of the people. God is not divided against himself.
No, God allowed the Jews to kill Jesus at the proper time. God willingly gave Jesus as a sacrifice, and Jesus willingly died as a sacrifice. Jesus did not have to die, he could have called on God to deliver him.
Mat 26:53 Thinkest thou that I cannot now pray to my Father,
and he shall presently give me more than twelve legions of angels?
Jesus didn't have to die, he willingly allowed himself to be taken and crucified. This is what was determined.
God did not determine that the Jews would kill Jesus. Satan tried to kill Jesus when he tempted him to leap off the temple, and at least twice the Jews attempted to kill Jesus, but Jesus escaped all three times. God could not have caused these attempts to kill Jesus because it was not the proper time. The devil and the Jews already of their own free will desired to kill Jesus, God only allowed them to do so on the Passover day.
God foreknew the devil and the Jews would desire to kill Jesus, but he did not cause this, God never tempts any man to sin (James 1:13)
You err because you do not know the scriptures.