They are all corruption, or corruption adjacent.
The plumber is working for a company. He's supposed to be working on an official job. But he's doing the work slowly because he's actually working on your plumbing problem.
You are working for the grocery store. You are stealing cheese from the store system that is supposed to allocate it, and making it available it to the plumber as payment for your plumber being corrupt on your behalf.
Again, the wife "who can help you get tickets" is stealing access to them. That's corruption.
The engineer who is tutoring, is paying for that act of corruption. This may or may not happen when the engineer is officially supposed to being doing something else as part of their job. If so, that's possible because people learn to look the other way for you, so that you'll look the other way for them.
And in a society where everything works this way, what do you think happens to overall economic productivity? Exactly! Which creates scarcity. Scarcity that makes the ability to get things through the blat network even more valuable!
None of that was specified. As I said earlier, the problem is not with quid pro quo; it's in the stealing which you've now specified as additional context. I could just as easily specify another context where each of these actions are legitimate. (Perhaps free tickets are part of the theater worker's perks.)
If I said "I baked a cake for my mother," then you could say "BUT YOU STOLE THE FLOUR!" It doesn't prove anything.
Would you say the scarcity is what starts the corruption?
Like you can't get a plumber so you have to use your personal network or there aren't enough tickets so you have to obtain one through your personal network, etc?