poison tongue - insidious misdirection

just a clarity question. this is used AFTER the decision of goes first correct?
i just want to be sure as this is one of those things people will argue over and could start a whole game off on a bad note if their is a disagreement.

Insidious Misdirection says:
"Use this Stratagem at the start of the first battle round, but before the first turn has begun."

The first battle round is the first sequence of each player taking a turn, so it is after any "before the battle" actions have occurred, including selecting first turn and seizing the initiative.

So yes, you can decide after seeing who has first turn whether you want to redeploy up to 3 units.

had another poisoned tongue related question. the whole re-rolling 1's thing also applies to their close combat weapons right?

It's right there in the Obsession wording. Yes close combat attacks too. Especially good for Lhamaeans.