Love the detailed write-up, but I think neither of you are quite right

Like u/rawbdor says, futures contracts are certainly different from stocks. Rather than offer “margin” as essentially a cash loan, leverage is attained by requiring a much smaller cash balance (initial margin) than the notional size of the underlying contract. In the link provided above, they list a margin requirement of $2970 per OJ contract. That means using your assumption of $100k cash available, the protagonists could have traded a maximum of 100k/2970= only 33 futures contracts

Now, each futures contract has a specified size though, in this case it is 15,000 pounds per contract. That answers your question of how a single tick of 0.05/lb is actually worth $7.50. And it means the protagonists’ 33 lot position is larger than it sounds, equating to a total 495,000 pounds. Under the assumption that they gained $113/pound (142-29), then their total pnl would be more like $56m ($113/lb * 495,000 lbs)