せんとする is a literary way of saying "to attempt" and you will not use it in saying something as casual as "What's this dude tryin' to say?"

I was wondering more about how you got the ことか part. It makes no sense when combined with せんとする.

Masaegu,

Quick question about something you said above. Regarding the "what's he trying to say" translations, you said they'd have a rising intonation at the end.

Let's take なんて言ってるのかな。
With the rising intonation it means "What's he trying to say?" like you expect an answer. If you say it without a rising intonation, does it sound like a rhetorical question asked to oneself?

Yes, it is. Among the two issues I mentioned last time, #2 is utterly unacceptable. A careful 4th-grader could have easily spotted it. It is almost like saying "To me she gave it to me." Remember I said "almost".

No, it cannot. No one but the speaker can say 気がする in the first place. If you used the pronoun "I", the particle can only be は.

If you use 気がする about another person, it will be a conjecture, not a real feeling that you are certain of.

Yes, exactly. You are talking to yourself.

"I wonder what he is trying to say."

EDIT: There has been a tendency in the last 10-20 years where some young people actually ask these questions with a falling/flat intonation at the end even when they are expecting an answer.

No wonder. Gibberish, period.

せんとする is the literary form of しようとする.

It has nothing to do with セントルイス but one can say:.

「セントルイスをより良い街にせんとする移民たちの努 力は実にすばらしいものだった。」　

Rikai chan is better for looking up nouns/adjectives/verbs, not speech patterns. Also, I generally wouldn't use Rikaichan for E -> J, only a quick J -> E. It's not good for learning, more for quick reference. If you want to actually learn, you should put it into a proper online dictionary with example sentences and all so you get a feel for the meaning of the word. A lot of times dictionary entries can be misleading without an example sentence.

Is the word "fan" commonly used in Japanese? Does it mean that, to become a fan of (something), would be expressed as "（something）のファンになります"? Is there keigo for なります？

"Fan"? No.
「ファン」? Yes.

「ファンになります」 is correct and there is 敬語 for なります. For every singe verb describing a human action, there is 敬語.

なられる
なられます
おなりになる
おなりになられる
, etc.