The way it's currently worded, landing on a rock means you still fully executed your maneuver, so as long as it performs a 3-5 speed maneuver a 2e defender still gets its evade action as long as it doesn't bump--even when hitting a rock. Is this correct?

Going by the rules reference, yes that is correct, but possibly only when going over or landing on a rock. As written, the only time that you don't fully execute your maneuver is if you overlap a ship. And since the action from the Ship Ability is not a standard action performed during the Perform Action step, you can take it even if you have to skip the Perform Action step.

The question I have is with Debris Clouds. Since Debris Clouds give one stress token after the Check Difficulty step, when is the maneuver judged as "fully executed"? I would say that the rules reference seems to indicate only the Maneuver Ship portion is used in determining if the movement was fully executed, which would allow Full Throttle to execute before Check Difficulty and so before getting the stress from the debris cloud.

However, I can see the argument that you must complete both Maneuver Ship and Check Difficulty before executing Full Throttle. If so, then deciding if Full Throttle is a game effect or not would become very important. I don't think Full Throttle is a game effect, so you would gain the stress first and then not be able to perform the evade action, but that's just my opinion.

Per the Rules Reference (page 13, under Maneuvers), executing a maneuver is moving, then checking for stress. For the entry on Obstacles (same page, 13), the check appears to happen at the same time for both asteroids and debris (after both "move" and "check difficulty" steps of executing a maneuver), regardless of differing game language for the two types.

In the case of TIE Defenders, they would roar through (or even onto!) a debris field, then check maneuver difficulty (and apply or remove stress as needed), THEN suffer debris consequences (take 1 stress from the Debris & roll for damage). After ALL of that, once the "Maneuver" was complete, "Full Throttle" would kick in and allow the evade action. Only if that Defender has a way to perform actions while stressed could they actually get that Evade action off.

You take debris stress "After the Check Difficulty step".

"Check Difficulty" step is part of "Executing a Maneuver", meaning "After the Check Difficulty step" is inside "Executing a Maneuver".

Full Throttle is "After you fully execute a speed 3-5 maneuver", wich is the same timing as "After you execute a maneuver". So you already have the debris stress when you reach this trigger.