Tolkien's Mistakes

[Legolas]

So according to this, Sauron built the foundations of Barad-dur, the lowest support of a tower, 600 years AFTER he began constructing it. However, after he did build the foundations, he built up the rest in only one year.

It's always a lot easier the second time you do something. He knew exactly how he wanted it, exactly how to get it that way, and so on...

Yet, the Mouth of Sauron doesn't seem to have anything against saying "Sauron"

I think this is something the Mouth is saying with purpose (against the usual) to show he is (as he thinks) second-in-command to the most powerful being in Middle-earth; it was an attempt to intimidate. This is a case similar to the avoidance of Black Speech (especially the name 'Nazgul'). Only Gandalf speaks the ring poem in Black Speech, and when he does, he strongly alarms others. Gandalf and Radagast are also the only characters that dare to speak 'Nazgul,' except for when Aragorn uses the term once in the safety of Minas Tirith after the Witch-King was destroyed.