No, you've made a good choice. fearImmune is something different than effective fear immunity, given by 110+ Bravery, right?
Q1.
Ehm, so I was wrong... fearImmune
does get pre-set for 2x2 units to "true".
Just like bleedImmune, painImmune and zombiImmune. But you can easily override it...
Also, fearImmune is a separate boolean attribute, not affected by Bravery. It was introduced by Yankes and if a unit has it set to true, their morale doesn't drop, ever, regardless of bravery.
Now, I have also used it to grant immunity to psi vision... since it wasn't used in piratez... but if you want a separate flag, no problem to do it.
Q2.
Unit A is looking at unit B.
1. If A and B are same faction, A can see B.
2. Otherwise, if distance between A and B is more than max possible distance (in piratez 40), A cannot see B.
3. Otherwise, if distance between A and B is less or equal to psiVision of A; and B is not fearImmune, A can see B.
4. Otherwise, if it's dark and max visibility of A (based on visibilityAtDark of A, activeCamouflage of B and predatorVision of A) is less than distance between A and B, A cannot see B
5. Otherwise, if it's day (=not dark) and max visibility of A (based on visibilityAtDay of A, activeCamouflage of B and predatorVision of A) is less than distance between A and B, A cannot see B
6. Otherwise, if there is no LoS between A and B, A cannot see B
7. Otherwise, if there is too much smoke between A and B (based on heatVision), A cannot see B
8. Otherwise, A sees B.
Hope I didn't make a mistake there
Ask if something looks suspicious.
PS: distances are calculated without considering Z axis