So, his round body fits with his past of being gluttonous. He levitates, therefore, the legs are undeveloped... lack of use. Overall design is dragon-ish as to what you originally intended him to be. The only thing I'd question is the inclusion of heterochromia.
"i made him his own original species to make up for it (it has no name) that are known for eating souls" - If nothing else, there's always the simple label of "soul eater."
A monster regretting its own actions despite needing to do so to survive has always been a compelling idea, but I don't think most media does a good job of resolving the matter... usually killed off early or the situation is resolved with some form of deus ex machina. I'm sure Toggle has a strong idea for Wak already in the works!