Ok so Carnor Jax would obviously kill any interaction from R4 Agromech - When you spend a focus token, gain a Target Lock.

Dark Curse makes the enemy unable to modify attack dice when attacking them, and Omega Leader is well... Omega Leader.

I would argue that they would prevent R4 Agromech from triggering at all if they attempt to spend a focus, even if it is to modify zero results. In the same way that you cannot un-Blinded Pilot if cloaked - you must meet all the criteria to attack and therefore ditch Blinded Pilot, and if you do not meet the criteria to modify dice, then spending a token would take you down a path to illegal modification.

Whether you argue it is zero results or not, zero results is still an amount to modify and as such you are not allowed to do that process. This part has already been FAQ'd. Therefore R4 Agromech cannot be triggered if the ship is attacking Dark Curse or Omega Leader when Target Locked by them.

Is my logic sound here?

Modifying All of Your <eye> Results when you have non <eye> results is still modifying, and Dark Curse and Omega Leader shut it down. Can't proc R4.

Yup. OL specifically calls out blocking token spending to modify all eyeballs in her FAQ entry.