Are the scarred parts of the stem due to cochineal scale (aka scale insects)? I am having a hard time resolving the exact cause of that stuff.
The insects are pretty easy to identify if you catch them in the act. They should be hunkered down against the skin, fairly firmly attached, but you can dislodge them easily with a sideways motion (using a toothpick or toothbrush or your tool of choice). The scar that remains is the exact size of the insect's body, including the hard waxy outer layer.
The adult scale insects lose their ability to walk once they are hunkered down, so removing them from their vampiric embrace means the end for them. However their progeny (probably invisible to the naked eye unless you're an advanced insect hunter) remain mobile, at least until they find a spot they like. So curing scale usually requires removing the adults and then spraying the plant down with 70% ethanol or insecticidal soap to ward off the youngsters.
The damage in the pics does not look like the scale damage I've seen, but that doesn't mean it isn't just some incredibly advanced infestation (now resolved, but having left scars). The important thing if you're pretty sure it was scale insects is to watch for the adults, which are immobile and easy to spot. If you don't see any bugs stuck to the plant, you can reasonably presume what you're seeing is simply their aftermath, and something the plant will grow out of.
I don't honestly know what else could be going on, maybe some fungal disease, but it's not anything I recognize. Try to be observant and see if the scarring is progressive. If it isn't, I'd leave it and concentrate on good care (making periodic stops to look for insects). This is what you would be looking for (camouflaged in the picture, near the base of the leaf):
The tiny growths are fruits. They turn purple when they are ripe. They are edible, like a berry, but only when really ripe.
The plant should be able to take lots of sun, pretty much all you can throw at it, provided temps aren't in the red zone. Morning sun should be great. Look for compact new growth to confirm you're providing enough light. Water well, to completion, and then wait for the soil to go dry most or all of the way at depth before watering again (not just at the surface, which dries out much sooner).
You do have the option of starting a new plant from a cutting, if you want to have something that's all green down the road. Maybe that would be good to consider once you're more comfortable you've got the care mastered, and we can provide step by step instructions.
