Merlin usually doesn't fix these sorts of typo's (of which there are many), especially if they're just comments or in modules that aren't used. They would need to be fixed upstream by Asus otherwise it becomes a case of whack-a-mole every time a new GPL is merged.
the Internet Speed on "Adaptative QoS" tab is not working well.
It gives me between 300 and 400 mbps down and using speedtest app or on site it gives more than 900 down.
I think you are wasting your efforts here. Anybody that does build from source would easily be able to fix all that up if they wanted to. You wouldn't just build the source like this just to apply an arbitrary diff file.