MTG Salvation

Hi everyone, I'm building a deck based on -1/-1 counters and I have a couple of questions for a possible scenario I would find myself in when playing the deck.

Scenario:

Let's say I have Soul-Scar Mage, Form of the Dinosaur and Nest of Scarabs in play. It is the beginning of my upkeep and I target a 6/6 creature with Form of the Dinosaur's ability.

My questions are:
How many tokens would I get from Nest of Scarabs?
How much damage would I be dealt from the creature I targeted?

My guess.

The creature gets 15 -1/-1 counters ALL at once, so you add 15 insects. Also you would not receive damage since 6-15 = -9.

Maybe I'm wrong, but I think it will go that way. If someone else can clearify my answer if there was something wrong, it's welcome.

That's my best guess as well. If someone else could verify or disprove that, it's welcome and appreciated.