1- by knowing those 3000 words can one be labled as a proficient?can he speak like a native?or he can only handle simple purposes in everydaylife?(supposing that he knows all of their usage, related phrases ,collocations and idioms)
2-how many words one must kNow to be proficient according to TOEFL? (TO GET 550AND ABOVE)
No- merely knowing the words does not translate into being able to use them. Most native speakers use only a few thousand words, though recognise many more. With 3,000 words, a person would be able to communicate at an advanced level if they knew how to use the words well, but would find simple tasks like reading a newspaper difficult because they wouldn't have the passive vocabulary to understand it all. It really is not a question of how many words you know, but what you can do with them, in my opinion.