One possible reason could be for protection. Maybe Naruto is hiding his true identity from an enemy who is specifically targeting him. He might be using the mask as a disguise to blend in and gather information without being recognized.
It's hard to say. Sometimes stories like this are inspired by real life but have fictional elements added. Maybe you need to look into the author's notes or background to find out for sure.
He could be hiding from Orochimaru. Orochimaru has always been interested in Naruto's power. Maybe Naruto has discovered a new power that Orochimaru wants even more desperately, so he hides behind a mask to avoid Orochimaru's detection.
Well, you could try doing things he likes together to strengthen the bond. Also, showing appreciation and support for him can go a long way. Sometimes, small gestures of love and care can make a big difference.
One way could be to have heart-to-heart conversations regularly, listen to his perspective, and work on resolving any conflicts together. Surprising him with small gestures of love and support might also make a difference.