Maybe 2.5 ‰ or so when I was 15-17, during a few parties where we used to play some drinking games and got too much of the hard stuff.
No one could ever hit 2.5%. You'd be dead well before you were halfway there. 0.25 is 0.25%, not 2.5%.
It's promille, not percent.
Is that how they measure it in Europe?
I don't know if there is a European standard, but, yeah, that's how we do it in Sweden at least.
I've no idea. I think my brother hit 2.9 promille once (so 0.29%). We know because he was taken in by the police.
I don't think I've ever been on any astounding levels.