The long wall of the tub is the outside wall. The mold you see in those pictures is not mold. However, there is mold in another location that I didn't show a picture of. I hadn't noticed it till you asked so I went to examine specifically for mold. I'm not sure the electrical outlet is actually connected to anything. I have not yet investigated that aspect. I was totally shocked to find it there. The tub had covered the outlet and the wire was actually inside (underneath) the cast iron tub.

Ripping it out is what I want to do but I don't know if it's what I should do. I have nothing against more work, I just want it to be an educated effort. I originally wanted to till the bathtub walls and tile the floor. However, I've since discovered it would take some major work to make the floor capable of supporting tile without ending up with cracks eventually. Since the house is essentially not nice enough for tile on the floor, I've lost my fire for putting it on the walls as well.