I've heard that if a presposition is 7 letters or longer, you should capitalize it.

Imagine these book titles:

"The House alongside Lake Michigan"
"The Cave underneath Mount Shasta"

Looks strange, doesn't it?

I would avoid the word "get" in very formal expository writing, especially in, say, scholarly research papers, legal papers or application essays for universities where you have a lot at stake - situations in which your credibility, grade or acceptance are on line.

If you have nothing to lose, or if your university writing requirements allow more room for creativity, go ahead and use "get". It's a multifarious word!

Yes, when "text" is a verb (i.e. send a text message), it's past tense is "texted". And I hear it quite commonly in everyday conversation.

When you see double prepositions, generally the first belongs to the phrase that precedes it and the second belongs to the phrase that follows it.

"This is something I want to invest in in the future."
"I plan to sit in on that class".
"Wind it up for me."

The use of "that" often makes the meaning of a sentence (especially a long sentence) clearer.

Consider two unique things; item A and item B. Item A is much farther from the norm than item B. In my opinion, you could then say that A is more unique than B.

Yes, it's "of the clock".

But the O' in O'Malley does not come from "of"; it comes from Irish Gaelic "au" meaning "grandson".

"I have an idea" and "I have an ideal" are both correct sentences. But the meanings are quite different.

I learned it this way:

If a word ends with S, you add apostrophe-S if you pronounce the S, and you drop it if you don't pronounce it.

"The cars' engines were running smoothly."
"The ladies' restroom is to the left."
"In Jesus' name, Amen."

but

"That is Mr. Jones's car."
"The boss's wife is attractive."
"There's a party tonight at Chris's house."

X is not S, so you must add 'S:

"Fort Knox's security system was compromised."

Modern proper names take 'S (Chris's, Jones's, etc.), but ancient proper names do not if they contain more than one S (Jesus', Moses').

Ah yes, the old debate over whether collective nouns are singular or plural.

So fat this hasn't been mentioned: In the US collective nouns (couple, team, group, band, etc.) tend to be considered singular, while in Britain for they most part they are considered plural.