"There is a table in front of me."
Hmmm, ok, yes, you can move the 前に around without changing the meaning. It'd be like if you started the sentences and suddenly realized you wanted to point out that it was in front of you. So in English your sentence reads like someone adding a thought to a sentence, "the table is, oh, in front of me I mean." It's not wrong it's just not proper or very fluid. The reason it starts with まえに is because then with context clues the speaker might be able to not say the rest of the sentence. If we were talking about where my car keys are in relation to the table you might simply say "in front of". Japanese prefer inferred meaning to spelling things out. So if you can answer simply with "in front of" that's ideal. Hence, 前に, direction, is first.
Is there a difference between the 一 (いち) and ー (symbol next to れ on my jp keyboard) ?
Some rather random experiments seem to suggest there is, but it seems weird to me as they appear identical. How would the second symbol be pronounced in isolation?
I understand that in テーブル it is used to enlongate the て sound.
The ー that is in テーブル does not have a pronunciation on its own. It is used to extend the sound of the kana before it. So in this case it extends the sound of テ by one unit of time (or mora). ー is used with katakana. The list [あいうえお] has the similar effect of extending the sound of previous hiragana.
We say [something]は...が... when we say something has a property/trait.
e.g. 私（わたし）は背（せ）が高（たか）い I am tall. 背が高い is tall. So I have a property of tall.
e.g. 東京（とうきょう）は人（ひと）がたくさんいます Tokyo has a lot of people. Tokyo has a property of a lot of people. We can say 東京には人がたくさんいます (which is better)
Now 私の前 is not a thing or concept that we take to describe a property. It is a location. So it is not natural to say 私の前はテーブルがあります. It has to have the existance particle に. It can be either 私の前にテーブルがあります or 私の前にはテーブルがあります. は is bringing the phrase 私の前に to a topic.
From what I gathered (from 語源由来辞典 http://gogen-allguide.com/), it seems before Edo period, these pronouns 貴様、お前 had the original meaning (honored you). In Edo period, people started using commonly among the public, and the level of politeness decreased. They even became rude in late Edo period.