Yes, you are changing the subject. Instead of talking about what the Scriptures say about eternal security you want to talk about what I would do in regard to a hypothetical situation which has nothing at all to do with eternal security.
You just refuse to face the fact that the Lord Jesus said that those to whom He gives eternal life shall never perish.
It has much to do with eternal security. The purpose of discussions about eternal security are to determine, before we die, whether we will live again in Christ Jesus--to give assurance to the believer. Your OP was asking whether the "all things are lawful for me" verses have something to do with eternal security.
If all things are lawful for all those who believe, and Judas was a believer, then even betraying the Lord Jesus was lawful for him. If he was not a believer, then it was better that he should not have been born. But in terms of people using their common sense to determine if they have eternal life, there seem to be one thing we need to check: do we believe on the Lord Jesus Christ? How do we check that??
Judas is an extreme case, and extreme cases are helpful in determining universal truth. If it applies in the extreme cases, then it more likely applies in all the cases in between the extreme cases.
So, with the purpose of discussions about eternal security being to either affirm or deny our eternal destiny, and eternal destiny riding on our belief in Jesus Christ, what does "belief in Jesus Christ" really entail?
We know that the demons believe and tremble--they know the truth about Jesus and believe it to be true, but it does them no eternal good. Why? I would suggest that it is because of a couple of things. 1. That it doesn't apply to them (no salvation is available to them), and 2. because they are not willing to do the will of God. Based on those two things, their destiny is the lake of fire.
What was the problem Adam and Eve encountered? They stepped outside the will of God when they ate of the the wrong tree.
What is it that God desires of His people? to be in His will.
What did Jesus teach us to pray? "God's will be done."
What did Jesus pray in the Garden? "Not my will but thine be done."
Why are there no adulterers and thieves and murderers and revilers, etc., etc. in the Kingdom of God? Because they don't do the will of God.
The whole purpose, as far as I can tell, of God when He created this world was to have a people that love him and are willing to submit to His authority. We can talk all day long about WHY God wants this, but if God is willing for anyone to do anything they want, that doesn't mean there is NO law. It means we are subjecting God to OUR law--i.e., everyone doing what is right in his own eyes.
So if everything is lawful, how is it that God wants so badly for people to obey Him? I'd say that the two things, belief in Jesus that is salvific and being
willing to obey (though not necessarily able), are not exclusive, but two sides of the same coin.