You do not need "g(lobal)" command here. You just need an address of lines for your substitution. Just remove it and you get an usual ex command pattern:
:ADDRESS CMD
Btw, try one cmd with a such...
Just a hint. "%" is an address for vi command to operate on. It is the whole file, but this address can be a regex (or line numbers).
You are doing very well and I don't want just to give you a...