Question about multiplying damage with decisive strike [duplicate]

So, reading another question about Decisive Strike, the answer was that it works the same as a critical, by multiplying its damage and therefore utilising multiple rolls and adding the totals, however, it’s still not fully clear to me.

Let’s say that in this instance a Monk 4/Swordsage 2 with Assassin’s Stance, Fiery Fist and Shadow Blade (let’s say the DEX bonus is +4) makes a decisive strike sneak attack unarmed on a monster.

Normal damage would be 1d8 via unarmed damage + 1d6 fire damage via Fiery Fist + 2d6 per sneak attack + 4 via DEX bonus

I know the example is convoluted but i helps me know which sources multiply and which don’t. As I understand, with decisive strike it would be the following:

2d8 via unarmed damage + 2d6 fire damage via Fiery Fist + 4d6 via sneak attack + 4 DEX bonus

Is this correct? Is the fixed bonus also multiplied (in this case the +4 damage for DEX)?

And also, one little question on decisive strike; it says that every other attack before the start of my next turn is also doubled, yet the penalty only applies to the first roll. Does this mean that any other attack I get to make this round (by, let’s say, Fire Riposte, or an AoO), also gets double damage without penalty?

Sorry for the convoluted question, but when I start reading supplementary manuals, even if they are the PHB2, things get more and more confusing. Thanks in advance!