1st The phrase, "May have eternal life." "May" means 'permission to' such as in the sentence, "You may come in." It does not imply that the person already is in or will stay in, but even though permission is granted, it still requires action on your part. "May" also means 'the possibility of'. Such as in the sentence, "It may rain today. "May" is not a word used to describe something that is definite or absolute, but possible. If you don't believe then it is not even possible for you to be saved, but if you do believe then it is possible for you to be saved. I can believe all I want that if I exercise I will lose weight, but believing it means nothing if I don't actually do it. And if someone said to me, "You may use my home gym so you can get fit." Does not mean that believing and having permission, in and of itself, makes me automatically fit.
You are speculating on the meaning of "may," apparently based on English; but the Bible is written in Greek. If you will quote a verse from the Bible we can discuss it. Similarly with the word "should." Generally there is no word in Greek "may" or "should" in such contexts. The subjunctive mood in Greek is sometimes translated using may or should in conditional sentences.
There are many many verses that offer salvation for believing or faith, where there is no "may" or "should" in it.
I give them eternal life, and they shall never perish. (No mays or maybes).
What must I do to be saved?
Answer: Believe on the Lord Jesus, and you shall be.
These are promises of God, no mays or maybes.
Then you go on, just opining things without Bible proof. If you quote verses, we may be able to discuss.
Believing is the only thing man need do to be saved. This is reiterated so many times in the Bible that the verses are more than a CC post box will accept.
Demons believe- does that mean they will inherit salvation? Absolutely not. (James 2:19).
That statement indicates a misunderstanding of saving faith. Saving faith is not believing
that something is so, it is trusting the Savior with this promise:
Thou shalt call His name Jesus, for He shall save His people from their sins.
A bit of the evidence:
Gal 2:15-16
We being Jews by nature, and not sinners of the Gentiles, yet knowing that a man is not justified by the works of the law but
through faith in Jesus Christ, even we believed on Christ Jesus, that we might be justified
by faith in Christ, and not by the works of the law: because by the works of the law no flesh shall be justified.
[NO WORKS, NO WATER]
Gal 3:
This only would I learn from you, Received ye the Spirit by the works of the law, or by the hearing of
faith?
3 Are ye so foolish? having begun in the Spirit, are ye now perfected in the flesh?
4 Did ye suffer so many things in vain? if it be indeed in vain.
5 He therefore that supplieth to you the Spirit, and worketh miracles among you,
doeth he it by the works of the law, or by the hearing of
faith?
6 Even as Abraham
believed God, and it was reckoned unto him for righteousness.
7 Know therefore that they that are of
faith, the same are sons of Abraham.
8 And the scripture, foreseeing that God would justify the Gentiles by
faith, preached the gospel beforehand unto Abraham,
saying, In thee shall all the nations be blessed.
9 So then they that are of
faith are blessed with the faithful Abraham. For as many as are of the works of the law are under a curse: for it is written, Cursed is every one who continues not in all things that are written in the book of the law, to do them. Now that no man is justified by the law before God, is evident: for, The righteous shall live by
faith;
12 and the law is not of faith; but, He that doeth them shall live in them. Christ redeemed us from the curse of the law, having become a curse for us; for it is written, Cursed is every one who hangs on a tree: that upon the Gentiles might come the blessing of Abraham in Christ Jesus; that we might receive the promise of the Spirit through
faith.
[NO WORKS, NO WATER]
Gal 3:22ff
But the scripture shut up all things under sin, that the promise by
faith in Jesus Christ might be given to them that
believe. But before faith came, we were kept in ward under the law, shut up unto the faith which should afterwards be revealed. So that the law is become our tutor
to bring us unto Christ, that we might be justified by
faith. But now that faith is come, we are no longer under a tutor. For ye are all sons of God, through
faith, in Christ Jesus.
[NO WORKS, NO WATER]
Gal 5:5-6
For we through the Spirit by
faith wait for the hope of righteousness. For in Christ Jesus neither circumcision avails anything, nor uncircumcision; but
faith working through love.
[NO WORKS, NO WATER]
Philip 3:8-9
Yea verily, and I count all things to be loss for the excellency of the knowledge of Christ Jesus my Lord: for whom I suffered the loss of all things, and do count them but refuse, that I may gain Christ, and be found in him, not having a righteousness of mine own,
even that which is of the law, but that which is through faith in Christ, the righteousness which is from God by faith:
[NO WORKS, NO WATER]
Col 2:6
As therefore ye received Christ Jesus the Lord,
so walk in him,
7 rooted and builded up in him, and established in your faith, even as ye were taught, abounding in thanksgiving.
[NO WORKS, NO WATER]
2 Tim 3:15b
the sacred writings which are able to make thee wise unto salvation through faith which is in Christ Jesus.
[NO WORKS, NO WATER]
Titus 1:4
to Titus, my true child after a common faith: Grace and peace from God the Father and Christ Jesus our Saviour.
[NO WORKS, NO WATER]
Heb 3:19ff
And we see that they were not able to enter in because of unbelief. Let us fear therefore, lest haply, a promise being left of entering into his rest, any one of you should seem to have come short of it.
2 For indeed we have had good tidings preached unto us, even as also they: but the word of hearing did not profit them, because it was not united by faith with them that heard. For we who have believed do enter into that rest;
[NO WORKS, NO WATER]