If I were asked these questions, I would answer only 1 and 2, because I am not an evangelical Protestant and the Q.#3 thus does not apply.
1. To a very large extent. Actually, exactly because I am an Orthodox Christian, I would NOT ever engage in any professinal business transactions, make a career in business. The way business transactions are being conducted in the modern world is, in my understanding, deeply, outrageously anti-Christian. The sacred Scripture so clearly, so explicitly prohibits usury, i.e. lending money to your brother and asking this money back with interest (Exodus 22:25, Leviticus 25:35-36, Deuteronomy 23:20, 21, Ezekiel 18:7,8,13; Luke 6:35). In the New Testament, these old prohibitions are not abolished, like dietary restrictions are, but re-emphasized in that you should not ask interest, OR EVEN THE MONEY (or anything else) you gave to a person, to be returned back to you (Luke 6:35, Matthew 5:40-42). And of course we are not supposed to amass material wealth, which is what the goal of business transactions is - instead, we are called to rid ourselves of all property, "sell everything and give the money to the poor."
2. Faith without works is dead. So, yes, of course, absolutely everything you do is important for your salvation.