'If I were'

[Fugitive1979]

Please correct me if I am wrong:

When I was young (here we use was as past form)
If I were an astronaut (here we use were as subjunctive form)

Correct.

[Pani]

Please correct me if I am wrong:

When I was young (here we use was as past form)
If I were an astronaut (here we use were as subjunctive form)

Correct.

So it should be: 'If I were you, I wouldn't treat me the way you do'.

[Your Funny Uncle]

Please correct me if I am wrong:

When I was young (here we use was as past form)
If I were an astronaut (here we use were as subjunctive form)

Correct.

So it should be: 'If I were you, I wouldn't treat me the way you do'.

Yes it should.

The idea of a "correct" form of English is actually historically debatable, though. Basically there have always been many dialects, and every so often the ruling elite tries to impose theirs on the rest of the populace as "correct". In the end, though, language is a constantly evolving thing so the concept of what is correct is a very fluid one even amongst the powerful classes. Contrast the way the Queen's early speeches with those of today and you can see that even "the Queen's English" as spoken by the our monarch herself has evolved over the last fifty years...