1) Spock having a positive relationship with his parents, particularly his mother, as a child, to the point that she read him Alice in Wonderland
And what makes this event uniquely "prime" timeline? It couldn't have happened in any other universe?
2) The USS Defiant ending up in the Mirror Universe
The problem with this is that we know that Defiant from "The Tholian Web" did not end up in the past of the mirror universe seen in "Mirror, Mirror" becasue the level of technology on the I.S.S. and U.S.S Enterprise was exactly equal, with the exception of agonizer booths and Mirror Kirk's special tantalus field.
The "Mirror, Mirror" mirror universe didn't have a 100- leg up on technology that the U.S.S. Defiant would have given them.
So again, we can conclude that neither "In a Mirror Darkly" or "Discovery" are part of the ("prime") timeline, becasue they majorly contradict what was shown.
Because there's no such thing as the "Disco-verse".
There was no such thing as the "Kelvin timeline" until there was. I don't think an appeal to the status-quo holds much weight.
Visual aesthetics aren't Canon because there's never been any one single unified visual aesthetic in the entire history of the Star Trek franchise; things have changed and/or evolved based on the technology available at the time of each franchise installment's creation and/or the whims of the creators of said installments.
Various consistent cross-era depictions, the largest being "Trials and Tribble-ations" speak to the contrary. While visual have changed in series depicting different era's, when those cross over into other depicted eras they are consistent.