I don't browse forums on my phone. I mostly use my PC. I would never sit in a dark room with a black PC screen, as it would make me feel anxious. I prefer bright screens and bright rooms.
No. Tattoos are objectively pointless and dangerous. Did you know that your body's cells try to eat the tattoo ink for the rest of your life and pass on the task to future cells and so on, because they see the ink as a foreign threat...
Then you must do your duty until the end. You did a great job and your sister is at peace knowing that you are a responsible guardian for her daughter.