I am not giving you the answers. I am just sharing some thoughts. A moderator or another member will soon give us the answers.
1. Some (many?) American speakers would have no problem with "If I was you, I would not accept that job."
a. But some people still use the so-called subjunctive "were." The subjunctive refers to something that is not true. I am not you, but if I were you, I ...
2, I think that your second sentence should not use "were."
a. Maybe it would be better to say something like: "If he had acquired the property five years ago [my note: he didn't!], he would have become a millionaire by now." Again this is a form of the subjunctive. Some people actually say: "If he would have acquired the property five years ago, he would have become a millionaire by now." Some people who believe in "good" English avoid such sentences.