Enemy can hear sounds from far away

[Romulator]

Haha, well kind sir you taught me about HearVolume.

Okay, the higher it is, the louder objects or stuff have to be in order for them to grab the grunt's attention. Toy with that as much as you want, remembering that the value you set there is what the MINIMUM sound volume you'll need in order to get the attention.

And no, that code is fine! The Model Editor way is just a way to do it with a GUI, so you don't need to open the .ent file, but what you did is okay too!

Edit (in response to your edit):
When editing the .ent file, a new one is created when you save, which has the values from the Model Editor in there. Just re-add it each time you make an adjustment, or check that you can't see it.

In the Model Editor's User Defined Variables for the grunt, the third or so option should be a Checkbox, which says AutoRemoveAtPathEnd or similar. Just uncheck that and you shouldn't lose your grunt