I inquired on a zulu forum about the tunic because I wanted to provide some variety in the command sets and my understanding is that the tunic was worn in the field as well as the patrol jacket. It certainly was in an iconic film. That said there are two different command sets of one disagrees.
Yes, everybody seems to wear the tunic in that movie. According to Ian Knight, though, the officer's tunic was not worn in the field. That's not to say your figure is wrong. It is pretty much impossible to button-count a 15mm figure, your boy could just as easily be wearing a frock. I can't see any buttons, let alone count if there are seven or five!
In many regiments the officer's frock even had white piping down the front (which the other ranks' ones did not), so there is absolutely nothing wrong with the figure as painted. I'm just nit-picking whether we call it a tunic or a frock.
Apparently it was also pretty common for officers to wear the other ranks undress frock, and it is thought that's what Bromhead wore at Rorke's Drift. Just to muddy the waters a bit more!