The word "apace" in this paragraph means "quickly" or "swiftly". The author is talking about birth rate declines, not only in the Western world, but all around the world; it is a trend that is not going to disappear or slow down anytime soon, and it is conquering the world at a pace that is becoming faster every moment. In other words, the trend is growing in speed.
Darth Vadar vs Luke Skywalker
The wolf vs 3 little pigs
Aladin vs Jafar
The tone Tony should use in his letter is the following one:
Objective and respectful.
His letter is addressed to a senator, a member of the government. Therefore, it is vital that Tony shows respect. At the same time, Tony must be objective, since the subject he speaks of is a very serious issue which has to be discussed in a very clear way, so Tony is able to make a point.
