Carnivorous Plant Question
A complex and detailed question?
I would say there is still hope for the Sarracenia. The problem is there is too much water. These are bog plants, which generally means they prefer very moist soils, but not where the water line is above the soil like you would do for a pond plant. And in a terrarium where the water is not moving, the water needs to be able to go down.
I recommend carefully tipping the terrarium over to get all the water out, holding the plant in place as best you can. When you water, add enough to let the water sit at the bottom just high enough to get above the charcoal and into the soil, and then let the water go down below the soil/charcoal line before adding more water.
Hopefully there will be new growth within a couple weeks.