I agree with what you said here, but the opportunity for being saved was opened to Judas just like the other 11, it is Judas that gave up not God on him.
I agree and disagree with your statement here. Judas never really "came" to Jesus nor did God really preserve or attempt to work on Judas heart as He does His sheep. If God wanted to preserve Judas like the 11 He surely would have. It is a true statement that God never rejects those who truly "come" to Him. John 6:35-40 would be a great explanation of sovereignty and the will of man.
The control of evil is by removing a hedge of protection or placing a hedge of protection, and how far it can go which means the hedge isn't completely removed. It does not stop forgiveness, it is open to all sinners even with the hedge of protection removed.
This is always open for us. We can take refuge in the Lord
Psalm 46
Devil can tempt us, but we are dragged away by our own evil desires
If God didn't have control then we would have already destroyed ourselves. Salvation is open to all sinners just as they are dead in their sin through Jesus Christ.
I think I agree with all you've said here. I do not believe there is ever a point on this side of eternity that someone can't turn to Christ, no matter how evil they've been. All people are wicked sinners to the core of heart and are in opposition to God (Romans 3 and Romans 8 are great examples). The only way a wicked sinner will turn to God is by the work of God within Him that makes Him willing. If God has elected someone there is nothing that can stop God's choice (Read Romans 8:30 to the end of ch.8).
I think it is interesting that Jesus told Peter that Satan could sift him like wheat. Satan did tempt Peter and lead him away with ease. Yet God chose Peter and saved him. Judas on the other hand was lead by Satan to deceive Jesus and God let Judas be. This isn't to say God pushed Judas away, but Judas was left alone in his fallen state.
I hope I didn't get to off topic...