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. 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; even as he hath said, As I sware in my wrath, They shall not enter into my rest: although the works were finished from the foundation of the world. For he hath said somewhere of the seventh day on this wise, And God rested on the seventh day from all his works; and in this place again, They shall not enter into my rest. Seeing therefore it remaineth that some should enter thereinto, and they to whom the good tidings were before preached failed to enter in because of disobedience, he again defineth a certain day, To-day, saying in David so long a time afterward (even as hath been said before), To-day if ye shall hear his voice, Harden not your hearts. For if Joshua had given them rest, he would not have spoken afterward of another day. There remaineth therefore a sabbath rest for the people of God. For he that is entered into his rest hath himself also rested from his works, as God did from his. Let us therefore give diligence to enter into that rest, that no man fall after the same example of disobedience. (Hebrews 4:1-11 ASV)Enter into the true Sabbath rest. It is not only for the "seventh day," it is for every day. It is not merely a rest from physical labor and financial gain, it is a "rest for your souls," a rest from dead works. It changes your heart, in a way that strict observance of the Sabbath day in Israel never did. And finally, it is an issue of faith, not of a manner of observance, as he says: "For we who have believed do enter into that rest."
And this is worth notice:
Seeing therefore it remaineth that some should enter thereinto, and they to whom the good tidings were before preached failed to enter in because of disobedience, he again defineth a certain day, To-day, saying in David so long a time afterward (even as hath been said before), To-day if ye shall hear his voice, Harden not your hearts.A "certain day" has been defined. Is it the "seventh day?" No: it is today, for as long as it is called, "today."
I agree with much of your post. Christ within us is a type of rest, but our rest isn't yet totally fulfilled until we are with Christ in his kingdom. The 7th day sabbath is not only a reminder of who the true creator God is, but also a pointer toward the rest to come.
Paul is actually confirming and expanding the sabbath for the Hebrew believers...he tells them:
Heb 4:9 So that there is still a Sabbath-keeping for the people of God.
The 7th day was blessed and sanctified by God:
Gen 2:3 And God blessed the seventh day, and hallowed it; because that in it he rested from all his work which God had created and made.
In all the bible, it was never de-blessed or de-sanctified by God.