[Imp]

I will take a shot at this

1- No unless you want to get a faster PC, the AI isconducting its turn, more units means more time. Just because you saw nothing does not mean it did nothing.

2- My guess is helos are closer than minimum range for the MANPAD's, they like some other types of weapon have a minimum & maximum range look at the unit info.
Could be many other things, no LOS no ammo.

3- Spotter LOS helps but planes attack what they see as a likely target near their target hex or as a good oportunity on the run in a reasonable distance from target area.
Plane picks target from what IT sees so more likely to spot large & or fast moving targets including mistaking freindly at times, low experience side is less likely to spot a suitable target so will just attack the hex targeted.
See threads about planes but generally dont attack near friendlys or fly over friendlys near target area. Depending on the weapon the plane can sometimes prefer to target hard or soft units.

4- Set points to max 65000 or something like that, set AI pointsto XX & buy what you want, AI gets correc points base on your purchase.
I would strongly suggest starting way smaller & learning the game mechanics before playing larger battles.