As far as I know, with decoy chaff used in this way, the chaff doesnt exist in the sim as a discrete object, but it is used as a factor in weapon endgame calculations. You can see the effect in the messages window if you have endgame calcs turned on. Essentially, if chaff is used (it is launched automatically if present) it is an extra dice-roll in the to-hit calcs. Its effectiveness therefore is not affected by the disposition of the ship. Basically if a unit has chaff, you have a slightly higher chance of dodging radar guided weapons, until it is exhausted. Same for aircraft.
You cant manually launch decoy chaff, so you cant really "get a unit in harms way" by improper usage. However, it is sometimes possible (weapon dependent) for a weapon that misses to hit a target beyond, but this is possible under any miss circumstances, not just those that involve chaff.
As far as I know, unit manouvre is solely evasive. Endgame calcs use relative target heading as a factor in to-hit probability, with head-on and tail-on being easiest to hit and 90-degrees side-on hardest to hit. The ship will also accelerate to Flank, as faster = harder to hit too. Wind and chaff do not affect the evasion manouvre.
There is a seperate use for chaff - aircraft can "dispense chaff", a seperate function from automatic decoy chaff, but uses the same on-board chaff resource. This type can be launched manually and appears as an object in-sim. Aircraft flying through this chaff are harder to detect with radar - they have their detection range decreased. Note that this technique is largely obsolete today, it will be most useful in scenarios set pre-1980 or thereabouts.
One thing I am not sure about is the difference between distraction and seduction chaff. I presume they perform the same function in-sim but Im not sure.