This is an expansion to "DarkVVind"'s solution
To expand on 2-1, the fastest I've done that level is 3:10 with a jet w/ pesticide for roughly 20k on inferno. Here's a summary. (It seems long and wordy, but once you try it a few times, it is easy.)
1. Go the right of where the tank will spawn. Wait for ants to spawn (Ops ends a sentence with "inbound"), then target the top gray trim of a brown building (right next to the white building on the corner.) That should take them all out.
2. Aim up/right for the carrier, shoot, and both should go down.
3. Jet toward lander, activate, activate.
4. Jet toward the next objective. Once you hit the river/ravine, turn around and snipe the the Hector.
5. Jet toward objective, ignoring everything in the way (they will hide once you get there).
6. Jump up on the "ledge"/ raised area behind the objective/crew. Turn around and look at the building that the ants are on. Snipe the top portion of building and that should get them all.
7. More will spawn behind that building you just blew up. Blow all of them up too.
8. Start jetting to the left, and once they are all gone, a mass will appear on the right. Zap them (either shoot an ant, or the white building on the left of the ants).
9. Then spiders should be popping up around you, go up the street at the gas station, toward the ravine.
10. Turn around, shoot a building to kill a wave a spiders.
11. There is another wave of spiders, take care of them.
12. A mess of spiders and a bomber-spider spawn. Snipe the wave on the left first while they are together, then get the bomber-spider.
13. Snipe the last spider wave.
Notes:
-AI is useless, so don't need them.
-My secondary weapon was the skillet just in case there was a straggler.
-It takes a while to figure out the blast radius; be patient.
-This is also good if you want to boost a secondary profile. They can live or die, and they are guaranteed 9720 xp. (In fact, I boosted 3 classes to level 7 while earning my money.)