"I have given him rules to live by but if he doesn't follow the rule book then I simply have to disown him as my son".
Christianity is not 'Do this, this, and this, or God will throw you into hellfire."
We naturally go to hell, it is our natural place to go because we're born sinful.
God saves us because He knows we are unable to save ourselves. We CANNOT work our way into Heaven, or earn it. It's not possible.
And once you're saved, you're saved. The Holy Spirit lives within you.
"I understand it's not his fault that he was born into iniquity - I mean he didn't ask to be but because one of his ancestors ate an apple, well that's just bad luck for my son"
If you have a child, you know he will disobey you and be rebellious. Should you still punish your kid when he acts up? Yes? But you KNEW he was going to act up at some point, and throw fits. So why punish him for something that you knew he was already going to do? Ask yourself that.
Or would you rather be an automonous robot without any freewill?
"Subsequently I have chosen to put him in a place where he will suffer and suffer for all of eternity."
no, sweety. Hell is naturally where we go, Hell is a place without God's presence.
Yahweh has not said, 'You disobey me and don't follow these rules, then I'm going to just throw you in this fire for eternity!"
Hell is where we naturally go if we aren't saved. Hell is a place without the presence of God.
If we're not saved by Christ then that is the only possible place for God TO put us.
God is love, God is peace, God is joy. If you're not with Him, what do you think the place you're going to is going to be like?
"If my younger son is tortured painfully and then hung up on a cross to die, I will feel so much better."
Jesus' sacrifice was necessary. It was terrible what He went through, words cannot fully describe it. But God died for us because of His great love for us. It shows how much He loves you, me, and everyone else.
"If my older son is prepared to accept that his younger brother suffered all of this pain on his behalf, then and only then, will I spare my older son from that eternal punishment"
Only through Jesus' sacrifice could we enter into the Kingdom of Heaven. We are born sinful and cannot save ourselves.
Yahweh is a righteous judge, He isn't going to let sin go unpunished.
So either we suffer from our natural sinfulness in Hell, or we're forgiven through the blood of Jesus.
"But his younger brother still has to suffer though, I couldn't possibly have it any other way"
No other way is possible.
"Does that make sense to anyone for me to do that to my beloved children?"
Based off of YOUR explanation, no it does not.