to point 2- that will work 100% things set to unagressive never, ever initiate combat, though depending they might return fire if fired upon (for example, enclave eyebots in FO3 were unagressive, so are pack brahmin in FO:NV)
The only slight issue there is that it works for setting turrets to not attack the player but they also won't attack anyone else then, they just don't attack. Finding a way to get them into the player's faction is the superior option, or you can apparently just set who the turret faction's enemy is and reset the AI and apparently everything is hunky-dory (see example from HV bunker below).
Also, here's how the game does it to turn off a turret:
ref myLink
set myLink to getLinkedRef
myLink.stopCombat
myLink.setUnconscious 1
This may help your targeting issue, this is the entirety of the code to make the BoS turrets target the brothers in the base, and not you:
; Make the turrets turn on the Brothers
SetEnemy BrotherhoodTurretFaction BrotherhoodSteelFaction
; Reset turret AI so they don't attack the player if they
; had targeted him/her before
HVTurret01REF.resetAI
HVTurret02REF.resetAI
HVTurret03REF.resetAI
HVTurret04REF.resetAI
HVTurret05REF.resetAI
I can give you more examples if that doesn't help.