But if he makes Sooin a vampire won't his blood not be the same anymore?

Yup

oh nooo, and then he’ll find another human that’s blood is sweet

This is exactly what i'm thinking!! For now idk... Let's just wish the best for both of 'em

Could this be a sign that he is starting to care about Sooin as a person and no just a blood supply?

I think he's not only care abt sooin, i think he started to have feelings for him too!

Definately!