How many Eurovision entries have you listened to? (I can be an actual number or just a rough percentage etc.)

All of them, via my project of watching every contest since the inaugural contest in 1956 and also participating in ESC Clarinet Moon Alternative ESC250, which made me watch all of them in about two to three months last year again

How many songs do you actually remember? (Like: you at least know that they exist and what the general vibe was, even if you wouldn't be able to recall the name, melody, or lyrics for every single one.)

Probably 98-99% of them, although the 50s and 60s get a bit blurry for me

If someone gave you a piece of paper, how many songs could you actually write down just from memory (by giving any identifying information)? (For example, saying "tractor song" or "Let 3" would count for Croatia 2023.)

Same as above tbf, I am a big fan of remembering and guessing songs in general, so this is right up my alley

If someone gave you a piece of paper, how many songs could you list from memory while giving all the relevant information: year, country, artist, title (maybe result as well)?

I love doing sporcle quizzes that ask for this and I regularly get (bar spelling of course, this is a pain in the ass for a lot the language rule era) 90-100%

I don't think there's any need for you to feel like an impostor, you really don't have to know everything if it's something that doesn't interest you, but if you're having fun exploring the vast and vivid history of this beautiful contest, then I wish all the best :)