So the Poison is penetrating too, right?

Yes, poison damage is penetrating by the wording of the power. Pretty brutal.

The pog is immediately ko'd after moving more than six squares away from negative man. I feel like I answered my own question but does this mean that if there is a character 8 squares away and the spirit goes to move through it for the attack afterwards, if the spirit ends it's turn within six squares is it still ko'd or can it make the attack?

Imidietly means you KO it when it moves beyond the five squares radius.
Do not pass go, do not attack.

If he gets flight somehow (Legion's Ring), gets Giant or Colossal or Negative Man gets Tiny he can carry Negative Man without beeing KOd???

Two year too late but:
When figure it remains on the map but in any specific square.
This mean that Negtive Man is not with 6 squares of Negative Spirit and the Spirit is KOed.

This is a crazy good BST, and is quite important for Doom Patrol teams. The Negative Spirit can provide actual offense, or can just get in the way of opposing teams. There is no shortage of Perplex on Doom Patrol figures, so the Spirit can pack quite a punch.