Stone’s Bridge
Riven in Stone
Stepping Stone
Came up with these before the Enough Already with the Stone! but maybe they convey the split, or the span.
Not to be pedantic (though I often am), why “in”? 
Riven Stone sounds cool!
File them away for future reference? You never know when they might come in handy! 
Leper. A leper in a hot tub. 
A play on “written in stone.” But I like “riven”, too.
Written in Stone is also good.*
*Not whooshing you here, honest! 
Given California, hidden things shifting under the surface, and good vs bad life choices, I think fault lines could work in a title, with the double meaning of “fault”.
"Stone’s Mystic Faultlines"
"Stone’s Secret Faults"
"Shifting Faults"
"Stone, by appointment"
"Malibu Stone"
Not “stone” related, and possibly a bit generic, but…The Primrose Highway?
It’s not my area of expertise, but you might consider looking up jewelers’ or diamond-cutting techniques and technology, which would surely have some peculiar industry vocabulary that could be scavenged for a title, or at least serve as an inspiration for one.
The only other idea I can think of offhand would be Free Stone, but that only mostly works if you’re making an oblique Frankenstein reference.
Personally, my own story-titling techniques tend just to be veiled puns, references to songs/poems, or both.
The Stone’s Path
Stone’s Portal
Hope you have some nice pens, and a blank book for your writing. 
Diametric
The Path Less Traveled.
From “Two roads diverged in a wood, and I —
I took the one less traveled by,
And that has made all the difference.”
The end of “The Road Not Taken” by Robert Frost. “The Road Not Taken” would be good title in itself and there don’t seem to be any books already called it.
Set in Stone
Bound in Stone
Stone Walls (as in “Stone walls do not a prison make\Nor iron bars a cage…”)
The Stone Stockade
Releasing the Stone
Everyone: appreciating the suggestions, but please, no more Stone titles. I think that one’s been sufficiently mined. 
Thanks!
Stone’s Stony Stones!
And we have a winner!!! :D:D:D:D
Is there some scientific term or phrase that means something like “at the point of no return” or “poised on the brink” or “could go either way”? That’s another possibility, if there is.
High Road Stone
Stone’s High Road
Paving Stone, as in the road to hell, or this case easy road, is paved, ie easier.
Epiphanic? The state of having an epiphany - learning something that changes everything.
Watershed - the moment that causes something important to happen
Spitballing here
“Event horizon” would be a point of no return.
“Crossing the Rubicon” or just “Rubicon” or “X’s Rubicon” or “Rubicon of X”
“At the Crossroads” or just “Crossroads” or “X Crossroads”
“When Push Comes to Stone” (Sorry!)
“The Crux of the Matter” or “X’s Crux” or “Crux of X”
“Moment of Truth”
Something about “poised,” or “balanced,” or having a tiger by the tail.
The Fulcrum in the Basement
The Stone Fulcrum (I’m sorry, too!)