ok so to verify you have an evar9 that is called "Video Category"?
Would I be right in saying you could have an evar designated to "Video name", you then want to use SAINT to create a Category group for it?
Also I see a little space in your code that could be tripping up things..
YOUR copy
header":[
"( 'Key','Video Category')"
],
DELETED extra space in front of key
header":[
"('Key','Video Category')"
],