While you’re waiting on an answer to your specific questions, let me add something from the perspective of a former controller…
We saw a LOT of deviations. Often multiple in one day. The majority were minor and we wouldn’t even bother bringing them up. Out of the rest, the majority of those were nothing more than a correction on the radio (e.g. “N123, verify level at eight thousand” when they dropped low, “N456, you were to go behind the Citation on taxiway alpha, not in front”, etc.).
Very rarely would we have somebody call us. Usually when we felt that safety was compromised or if we needed to talk more than we could do on the radio. I feel like I personally saw it maybe once every 3 months, if that. Fun fact, the “possible pilot deviation” statement giving you a phone number is called a Brasher Warning. Maybe the first guy to get caught screwing up was named Brasher. I dunno.
In every single one of those cases, the supervisor would educate/chew out the pilot over what happened, and that was that. None were passed on to the FSDO for follow up, to my knowledge.
Except for some unusual cases, it’s ATC who will be the ones who become aware of a deviation, and they are not the sky cops. They just want you to fly safe. Unless we had reason to suspect that a deviation was intentional and reckless, I don’t know anybody who would turn it in (unless we had some other compelling reason to do so, like an accident occurred because of it).
I’ll add that this is just my personal experience, but it’s over five years in multiple facilities, so I feel that it’s fairly representative of what you’ll see. Apologize, acknowledge your mistake, learn from it, and that’ll almost certainly be the last you’ll hear about it. And don’t it again, of course.
Oh, last thing… from what I know about the FSDOs, their preference is also to educate and counsel first. Enforcement action is scary, but they just want you to be safe. So if you do get a call from them, own up and don’t be evasive about it. Enacting penalties is more work than talking it over, so… make it easier on everybody and admit up to any mistakes. From what I’ve been told by FSDO friends.
Edit to add: I know there are a lot of good arguments to not volunteer any extra information should the FSDO call you, to lawyer up, etc. The last bit was just repeating what a friend from the FSDO said. Take it as you will, YMMV.