Some linguists, such as Albert Thumb, argue that the vocative form is not a case but a special form of nouns not belonging to any case, as vocative expressions are not related syntactically to other words in sentences. Pronouns usually lack vocative forms.
Yes, they are still grammatical cases.
That depends on who you ask.
https://en.wikipedia.org/wiki/Vocative_case
It seems in English speaking countries it is treated like a case, in Germany it isn’t.
I’m just shitposting, amigo. I wouldn’t worry too much about it.
The point stands that most english speakers would be confused by grammatical case since english doesn’t have that feature.
English pronouns still have case
Yes, we do. Just not in the same way that latin does. Ours is only for pronouns whereas they declined every noun in crazy ways.