At some point (especially in the hanger right before they escaped), sure. But I seriously doubt it [troops missing on purpose as to track them to the rebel base] was happening from the second they landed on the Death Star. That strains credibility by quite a bit.
No, not right away. But as soon as they bust the Princess out, I’d say the plan was made and orders given. The only scuffle before that is when Luke n’ Han are dressed as troops and take em by surprise.
Maybe I’m wrong and they are supposed to be terrible with aim and the whole thing is supposed to be silly, that’s just not how I see it.
First thing Vader says after they board the Death Star is “They must be trying to return the stolen plans to the princess. She may yet be of some use to us.” After they’ve freed her, I agree that they are letting them go. It is maybe not supposed to make you think about it when watching it as a movie, but if the main two guys in charge on the station have made a plan and installed a tracking device to lead them to rebel base to destroy the whole rebellion, it would be the most stupid thing to have some bumbling troops to ruin the whole plan.