Thanks! Perhaps my observations will be useful to you.
1. Su-25 was not destroyed with 1 bomb, although it fell apart. I applied 1 more maverick.
2. I initially sent a follower to destroy the Su-25. But then he canceled it with the command "return to duty".
I will add that in mission 3 the helicopter circled near the lake at point 2. I even destroyed 2 towers. But the mission didn't want to continue, I just destroyed the armored vehicles at point 3. The scripts started working further and I went through the mission normally.