Harm and harm moves

We played a demo some days ago and we had a doubt.

On p. 65 there is written:

When you take harm, the Keeper will tell you what happened and how many points of harm it was. Mark off that number of boxes on your harm track. There might be an additional effect: the Keeper will tell you if there is.

Then, on p. 135:

Every time someone gets hurt, use a harm move on them.

So, how the Keeper has to play with harm and harm moves?

Moreover, (again on p. 135):

Injuries allow you to make harm moves against that hunter (or monster, minion, or bystander), based on how bad it is. Every time someone gets hurt, use a harm move on them.

The harm moves are listed below, along with the minimum harm level for each.
0-harm or more:

• Momentarily inhibited.

• Drop something.

• Take -1 forward.

1-harm or more:

• Fall down.

• Take -1 ongoing.

• Pass out.

• Intense pain.

Unstable wounds:

• +1 harm.

8-harm or more:

• Dead.

Since only hunters roll dice, I assume the Keeper cannot choose the “Take -1 forward/ongoing” options for monsters, minions and bystander. Right?

A last note (this is a question the players asked me): why to “complicate” the harm rules this way, giving the Keeper so much responsibility and work on them?

Whoops, I forgot to ask if +/- 1s forward and ongoing sum one to another.

I.e. I have +1 forward and +1 forward, then do I take +2 forward?

And is there a maximum/minimum bonus limit?

Since only hunters roll dice, I assume the Keeper cannot choose the “Take -1 forward/ongoing” options for monsters, minions and bystander. Right?

Correct.

A last note (this is a question the players asked me): why to “complicate” the harm rules this way, giving the Keeper so much responsibility and work on them?

It's there because I wanted there to be some definite effect in the game from taking a hit, beyond ticking off a harm box. It doesn't give the Keeper any more responsibility than they already have (except that there is an extra set of moves to use).

And yes, forwards can add together to give a larger bonus or cancel each other out.

So, as a Keeper, can I choose to not do a harm move, or when someone takes harm, have I to always do a harm move?

Do it every time you remember. But if you miss some, it won't break anything.

As with everything else, it's there to support the agenda and principles.