Can I use cactus juice to stabilize leather? If so what is recommended as far as soak time? Has it been tried to your knowledge? If so any pointers?

I have not personally done leather but I do have customers who have with good success.  There is no way to give vacuum or soak times since there are too many variables involved.  It should be treated just like wood or any other porous materials.  Vacuum until the bubbles stop coming of of the leather, then soak twice as long as you pulled vacuum, minimum.