Missed this, wow, interesting plant.
I wouldn't go by an app for watering. What did it recommend?
I'm guessing the stem has gone south, it just looks squishy, and the black oozing is disconcerting.
I'd consider removing dying leaves, let it dry out a bit, check the roots.
Even if they're okay, I don't think that stem's going to function much longer.
Consider rooting the top portion that has growth if you have a chance.
Hopefully purpleinopp will have some input.