Nando,
 
I agree with much of what you say but have to disagree with your conclusion, where you said:
 
[My comments in brackets.]
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Jesus gave His life to pay the penalty for all your sins and rose again to show that His payment was sufficient (Romans 10:9).
As soon as you believed that you became as righteous as He is.
 
[This statement I believe]
 
There’s nothing you can do for good or bad that will ever change that
 
[But this one I disagree with.]
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Yes I believe that it is the gift of righteousness that puts us all in right standing with God through faith in Jesus' substitute for us but you seem to suggest that once a person has believed and received this gift that nothing he does can separate him from it again. You see, it is not works of the flesh that are being focused on, at least not by me, (though I agree with you that many do wrongly focus on that as the deciding factor). You and I agree that those kind of works are not what makes the difference, for all the reasons that you quote from scripture.
 
But I believe that you go too far to suggest that therefore since righteousness is a gift of God, that we can never lose that gift or forfeit the good standing. It is not by works but it is by faith and faith CAN be abandoned. The gift of righteousness is given for our faith and the condition that that faith is held onto and maintained against all temptation to abandon it. Just as the children of Israel in the wilderness stopped having faith in God to deliver them and they (except Joshua and Caleb who did maintain faith) were destroyed by God. Or just as Rahab was safe as long as she and her family stayed in her house, through faith in the covenant made with the Israelite spies, while Joshua and the Israelites fought against them. If she would have left that house she was vulnerable to whatever evil came her way. In the same way, as long as we remain in Jesus and hold onto the belief that you have quoted about then we are safe and God does credit us with Jesus' perfect righteousness. But if we leave off trusting in that and turn to anything else, including works of the flesh, then we are not in the faith and the gift no longer applies to us. Do you see this? The reason that the narrow way has few is because so few will stay faithful to this promise. So many go off into works or some other false belief and they forfeit the gift of His righteousness. That is why Jesus said when He comes shall He find faith in the earth... Apparently He knew that there wouldn't be much by then. (He didn't say shall He find church-goers or even Christians but faith.) Hebrews says we are His if we hold fast our faith firm unto the end. It says that this faith is our title deed to the kingdom of God and urges us not to lose it but hold fast to it. It is possible to leave the faith and make shipwreck. But this is not the same as saying that you can miss the rapture due to lack of enough good works of the law or of the flesh. If there are some who say that then they are wrong as you have said.
 
I believe that there is powerful insight to all of this in the account of Moses who saw the promised land with his eyes but did not enter it alive though he argued with God about it. I believe Moses was a type of those who will miss the rapture though they see it with their eyes they will not enter it alive even though they will also argue with Jesus about it (Lord, Lord...) but they will have to die to get in just as Moses did. Why? Because Moses struck the rock which was Christ the second time instead of speaking to it by faith as instructed in Romans 10. To strike Christ the second time is referred to in Hebrews as crucifying to oneself the Son of God afresh or the second time and is what one is doing who returns to the works of the law after having been saved by faith in Christ's sacrifice.
 
Nando you are correct that works of the law cannot save us but you must understand that those who do seek to be righteous by the law are guilty of breaking the whole law when they try to keep it and fail. According to Paul they are debtors to the whole of the whole law then because they seek to keep any part of it. This is because they don't believe that God already credits them with Christ's righteousness simply for their faith. Oh that's too easy! So, what I am saying is that ironically some of the very people who teach that you must be doing enough good works to be raptured are likely to be among the left behind because their works do not add up high enough to reach heaven. Jesus described them as seeking to build a tower (of Babel) and said that they will not have sufficient to finish (just as that tower was never finished) and all who behold it will begin to mock them when they miss the rapture. He advises that we stop the tower building and put Him first in our life, or become His disciple because then we will be in through His righteousness. Once we know that we are sinners according to the law and go to Christ we have graduated from the law and are no longer under it because it was our schoolmaster to drive us to Christ. But if we through ignorance and bad doctrine return to the works of the law then at that moment we have left off faith in God's promise and are back under the law and God must judge us by how well we keep the law.
 
Romans 10:
4.  For Christ is the end of the law for righteousness to every one that believeth. [No longer under the law if you believe.]
 5.  For Moses describeth [when he struck the rock the second time] the righteousness which is of the law, That the man which doeth those things shall live by them. [If you seek to be righteous by the law you will live by your success or failure of the law and fail is all you can do.]
 6.  But the righteousness which is of faith speaketh on this wise, Say not in thine heart, Who shall ascend into heaven? (that is, to bring Christ down from above:) [In other words, you are seeking to help Jesus save you by helping to get Him down from heaven.]
 7.  Or, Who shall descend into the deep? (that is, to bring up Christ again from the dead.) [Again you help Jesus save you by helping Him rise from the dead - He didn't need our help to do those things so He doesn't need our help keeping the law either.]
 8.  But what saith it? The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach;
 9.  That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. [Just speak to the rock and be saved and don't strike it again. Don't try to keep the law. REST IN HIM!]
 10.  For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
 11.  For the scripture saith, Whosoever believeth on him shall not be ashamed. [Believe on Him and you won't miss the rapture but stop believing on Him and you most certainly can miss the rapture and be ashamed.]