Okay, I added my BPC Dialogue child via “Add Component” to both my ItemBP and my PlayerBP and it works perfectly now. I can breathe again. Thank you very much for your support.
Also, I should probably mention that you were right earlier about variables not working on row 0 of the data table. You HAVE to create an empty first line and silence it. Otherwise the first line of dialogue will always be shown, regardless of the condition. Definitely sounds like something that should be fixed, or at least mentioned somewhere.
Now I can get back to figuring out how to fix that nasty mid-word line breaking. (Yes, I am that guy from Youtube.)