May I be so bold as to recommend instead of gluing, which doesn't seem to be working, to do something that will strengthen the wrist and ensure you can go Elk Hunting with it and it won't break when you do?
BTW, I repaired a far more damaged and actually shattered wrist on my Pedersoli Brown Bess Carbine doing much of what I'm about to describe and no problems ever again even when shooting those punkin' size round balls.
Since it has cracked in two pieces rather cleanly, I would drill into both pieces to form a long hole so you can use Accra Glas Gel and a piece of 1/4 inch diameter brass "all thread" rod as internal strengthening. (I had to use two 1/8" rods on the Bess to get around each side of the "Thumbpiece" or Escutcheon Screw that goes vertically through the wrist.) I prefer Brass because it is closer to similarity of wood, but you can also use Iron/Steel all thread rod.
By drilling (inside and parallel to the wrist) from the crack towards the front and drilling from the crack towards the rear and at least a couple of inches into the heavy portion of the buttstock, the hole will never be seen and you don't have to worry about messing up the breech inletting to drill through there for the rod.
I also used what I call an "Internal Dove Tail" with it. I originally got the idea from a "dutchman" repair used on furniture. You sort of wallow out the inside of each hole a little so it stays close to the same diameter near the crack, but it gets larger and sort of cone shaped internally on both pieces. Something like an hour glass laying on it's side and the center/small portion of the hour glass is centered on the crack, though you don't waller the wood out near as much as an hour glass on each side of the crack.
If you are interested, I have more tips on how to do it.
Gus