seems that u lost hope in the fish, just sell it if u not willing to spend more effect and time on it and get ur money back, the fish need a right owner who really likes it
datnoids can be really annoyin in that sense... have u tried putting him in a diff environment? ive had it before where a fish will b totally unstable n eating very irregularly... n then i put it in a diff tank or totally change the layout/interior of the tank and magically they would start eating well