
i love this story
but, may i ask which one is better, novel or manga? that can describe all yuuri and wolfram's feeling

the novel is better

Googling Kyou Kara Maou novels would give you the link you need, but... yes, sure:
https://www.baka-tsuki.org/project/index.php?title=Maru-MA

I wonder if Bum's legs can heal or not

I'm not a doctor, but I have broken a few bones in my life so here is my guess. After a few months his bones will "heal", but it will not be set correctly without a cast and considering it was broken with a bat it would more than likely require surgery for the bone to heal correctly because the bone will be in shards. More than likely if he does get to a hospital, he will be lucky if they can re-break the bone and set it correctly. What I fear is that they will never be able to reset the bone properly because of time and the degree of the break leaving the poor boy handicapped for the rest of his life.
Wrong tag, it's yaoi not shounen ai, please fix it