It think there is still a lot we don't know about how his thingie works, but I guess he needs to be the one making the touching.
And about the doggie, well, I don't know, maybe he can learn to control it, or maybe it only works sometimes... I really have a lot of questions too, but I think we will get our answers at some point.
I think now the living being gets older if Dam touches the living being when it's watered or something like that. Just like what happened with the bird idk
Yeah, I think water can be a possible trigger since it's occurred multiple times throughout the story where plants would grow when he adds water, same with the bird, but it's not 100% confirmed. As for Mishee, Dam said that it looked like the boy was in pain, so he probably purposely made his body grow.
how come the other people around dam dont grow older when they touch him anymore? cuz mishee grew a lot as well as the person who died at the beginning? im kinda confused or maybe i missed smth