Seems like there's just no information available at the present time - wondering if somebody could answer a few questions.

Could somebody clear up in plain english exactly what a mod is and exactly what a mutator is? Do I need to create a mutator to have a mod? Do I need to create a mod to have a mutator? Are they the same things? What are rulesets? All these terms seem to be being used interchangably from the point of view of an outsider looking in. (My experience is with Unity, this is miles away from my comfort zone.)

Something super simple first - let's say I want to sort the M249 out and fix the joke recoil.
I:

1. Load up the SDK.
2. Press the create mod button, fill the form out.
3. Locate the M249 and its handling files.
4. Change the recoil numbers to numbers which make sense in relation to other weapons.
5. Press the button to compile the mod and to upload it to mod.io.

This doesn't work. The server says it loads the mod, but the M249 still reaches for the sky the moment the trigger is pulled.

There's so much which is undocumented, combined with so much bugginess I hardly know where to start.

Anyone want to offer any assistance or point me in the right direction?