(I guess we're doin' this.

)
It's not so much a sticking point as it is a glaringly loose end that 98+% of Christians refuse to tie up.
What about the copious amounts that recount Jesus trying to teach His people how to keep it correctly.
Why would He do that if He was getting ready to just -86- it?
And what in the world are "Christian scriptures?" Do you mean the ones that Paul and Peter and Jesus used to teach the New Covenant?
Aunty, I take you as being a little too intelligent to be using a sophomoric argument like this against the Sabbath. And that's no back-handed compliment, either.
Well before about 1980, at least 90% of Christians would have answered this question like this:
Exodus 20
8Remember the Sabbath day by keeping it holy. 9Six days you shall labor and do all your work, 10but the seventh day is a Sabbath to the LORD your God, on which you must not do any work—neither you, nor your son or daughter, nor your manservant or maidservant or livestock, nor the foreigner within your gates. 11For in six days the LORD made the heavens and the earth and the sea and all that is in them, but on the seventh day He rested. Therefore the LORD blessed the Sabbath day and set it apart as holy.
But now that the Old Testament has been retired, I'd probably go with this:
Circumcision is nothing and uncircumcision is nothing, but keeping the commandments of God is what matters. (1 Corinthians 7:19)
I can't help but suspect that you know who is being referred to here as "God."
Jesus did this but Paul said that...
(And John said <see below> and James said, etc., etc., and on and on)
I honestly don't understand all of the resistance to the 4th commandment.
It truly boggles my mind. It's a surreal decades-long moment.
When I was a kid, nobody I knew or heard of (and my dad will bear me out on this, because he was always 20 years' worth more aware than I, and a world traveler) was trying to reason their way out of keeping the 4th commandment. They were just mixed up about which day of the week was being addressed.
I honestly don't get it.
Unless, the world has crept into the church with its anti-authority mentality, which I cannot but highly suspect, giving the eyewitness evidence to which I am privy, but which so many others of my generation either missed, ignored, deny, or were themselves artfully deceived.
How is the 4th commandment a shadow of the life, death, and resurrection of Jesus Christ?
I can't say for sure, but I'd conjecture that if you look into the mid-20th century archives of Witness reading material on this subject (if there are any) you won't find this kind of anti-Sabbath reasoning or sentiment.
You can just imagine, what with it being a central focal point of the moral code for human beings, etched by the finger of Jehovah, the Creator of human beings, on tablets of stone amidst thunderings and lightings and other scary stuff, and all.