It's natures way of telling you created a weak point.
As you move outwards along the limb the increased thickness section has to start before the limb narrows, it's a tricky transition that has to be smoothly blended. If you narrow the width too abruptly with no extra thickness.... well you can see in your pics what will happen.
It may be salvageable and even if it isn't it's good experience.
1. Plane off all the extra thickness, where the split has started, leaving a thin lever.
2. Stick the end in boiling water, steam or dry heat and pull it back in line.
3. Make a new vertical section, with one wide end and glue it onto the belly side of the thin lever, with the wide end overlapping onto the full width limb.
4. Blend in the new lever... leave the glue twice as long as necessary, then test it.
5... you may want to do the other lever too.
Even if it fails it will improve your patience and your skills.
I've done that repair before, but I did it before it failed
.Details here:-
https://bowyersdiary.blogspot.com/2015/10/stitch-in-time.htmlDel