とする(か) VS Volitional, conjectural and と思う

Question

The speaker just finished preparing a ring for a tournament when he says this sentence by himself (there is no hearer in the scene) :

さて...テレビ局に行くとするか。

I know that とする can mean "to decide to", like にする, the sentence would then mean :

I (just decided that) am going to go to the TV station.

What difference is there between the volitional form 行こう and 行くとする when it means "to decide to"?

If とする means "to suppose", "to assume" then the sentence would mean :

I guess I am going to go to the TV station.

Which makes more sense to me because of the か which I guess adds a bit of uncertainty which wouldn't fit (to me) with the meaning "to decide to".

What difference is there between the conjectural 行くだろう(か？), 行くとするか and 行くと思う(か？)when it means "To suppose"?

Bonus point for a quick explanation of this か that I seem to find everywhere.

Answer 1

It appears that you may be overanalyzing the phrase a little bit.

「(Verb) + とするか」 is a set phrase that one says to oneself meaning:

"Time to (verb)!" or "Gotta (verb)!"

You do not need a listener to say this even out loud, either.

"I know that とする can mean "to decide to", like にする, the sentence would then mean :

I (just decided that) am going to go to the TV station."

「～～とする」 and 「～～にする」 that mean "to decide to" have very little to do with 「～～とするか」. There is a grammar difference between the two as well.

"to decide to (verb)" = 「(Veb) + こと + とする」 or 「(Verb) + こと + にする」

"Time to (verb)" or "Gotta (verb)" = 「(Verb) + とするか」 without using 「こと」

This difference with 「こと」 is huge as it changes the meaning and usage entirely.

"What difference is there between the volitional form 行こう and 行くとする when it means "to decide to"?"

This question could not be answered because 「行くとする」 does not mean "to decide to go" even if you wanted it to mean it. Instead of saying 「行くとするか。」, however, you could say 「（そろそろ）行こうか。」 to yourself. That would be a fairly natural choice among us native speakers, too. Another choice would be 「（そろそろ）行くか。」.

"If とする means "to suppose", "to assume" then the sentence would mean :

I guess I am going to go to the TV station."

I think it safe to say that the meaning of "to suppose" is included in the phrase 「(verb) + とするか」 even though that is not the meaning of the phrase as a whole.