Learn English – Grammar: the function of “so” after conjunction

They are both okay. You can conjoin any two phrases of the same type to get another phrase of that same type. The structure is

I am doing this [[to [get more attention]] and [to [seek for opportunities]]].

where "and" connects two to-infinitives and gives you a to-infinitive that goes with "doing this". But the two lower verb phrases could also be connected:

I am doing this [to [[get more attention] and [seek for opportunities]]].

giving a verb phrase in construction with the "to".

There are no special rules for rarely used prepositions. According to the Chicago Manual of Style, all prepositions should be lowercased (except when they are stressed or occur as the first or last word). But I hardly ever see this style used. The AP style is much more common. According to the AP stylebook all prepostions containing three letters or fewer should be lowercased, while the Wikipedia Manual of Style says all prepositions containing four letters or fewer should be lowercased.

However, the Wikipedia rules are not enforced, and as a result the capitalization on Wikipedia is a mess, and often in violation of the style manual (as you had observed). I think the reason for this is that the AP rules are dominant in real life, so this is what people are used to (i.e., what “looks right”). This explains many of the cases that you listed: down, over, unto, upon etc. are all capitalized according to AP style.

So regarding your examples, it depends on the style guide you choose whether the four-letter prepositions should be lowercased. Three- or two-letter prepositions like on, off, out or up should always be lowercased (if they are really used as prepositions and do not occur as first or last word). Yet should also be lowercased, if used as a conjunction.

There is no difference between book titles and song titles. The AP style for instance says that its composition title guidelines apply to book titles, movie titles, opera titles, album and song titles, radio and television program titles, and several more.