Yes. My Demon originated from a manhwa and has made certain changes to fit the medium of the adaptation. But the core elements and storylines are drawn from the manhwa source.
No. 'Manhwa' is a form of Korean comic or graphic novel, and it's not something that can be eaten in a literal sense. And in the context of leveling up in games or personal growth, consuming a manhwa novel as food is an absurd concept and has no real way of contributing to leveling up.
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.