So, I think this 3 turn route is about as safe and repeatable as it gets. First off, I'm using alt f4 and space to skip to the 5th try of this mission, where a crate spawns allowing you to get a triple in the first turn. And there doesn't seem to be any other way to get a triple like this.
Turn 1: Grab the 2 crates, then bat the worm to get a triple. To memorize this angle, it's the first sprite change above the 45 degree position, then 1 more notch. My worm ends its turn in a spot making the AI guaranteed to hit my 2 worm pile/walk right.
Turn 2: Just a bat to pile, doesn't have to be totally exact. I tend to walk left on retreat, which I believe makes the AI more likely to pick the right two worms as targets next turn.
Turn 3: Just double damage and airstrike, I've found aiming left best. Now here, it's assumed the AI worm will have walked right. Depending on wind though, it won't do this 100% of the time; at least I'm not sure there's a way to ensure this. I think later I'll include what we might do in this case, though we may have to just say the run is no longer viable if that happens.
Possible Improvements: There may be some way to force the AI right every time, but I'm simply not sure.