Learn English – “for”as a preposition sometimes can be interchangeable with “because of”

Here's my opinion of your alternatives.

1. "because" is your best choice for clear, correct, unambiguous communication, especially if you want to be understood easily by other non-native speakers.

2. "since" is acceptable, although it makes your statement ambiguous; the second meaning would be that statement A became true at the time that statement B became true. Example: "I study more often since I enrolled in class" conveys that when you enrolled in class, then you began studying more often. Rule of thumb: prefer "since" when your intent is to convey "from the time that".

3. "as" is somewhat acceptable, but in your particular statement structure "as" has more useful meanings of "abstractly analogous" or "synchronously". Example: "I like apples as you like oranges" conveys that my liking is similar to your liking, i.e. equivalently strong/weak/notable/etc. Example: "I make dinner as you set the table" conveys that we do these tasks at the same time in the same place. Rule of thumb: prefer "as" when your intent is to convey "sameness".

4. "for" can be acceptable, although I would never expect to hear it in normal conversation. It would come across as overly-academic, or possibly epic or religious. Example: "We eat well tonight, for tomorrow we go to war." Rule of thumb: prefer "for" when you want to be poetic and inspirational.

Sadly, the most influential book on English Grammar does not accept the unqualified statement Prepositions are followed by a noun phrase or pronoun. It accepts the idea of the subset of 'intransitive prepositions' which are obviously not followed by a noun phrase or pronoun, citing the similarity of structures such as:

He had never been abroad before the war.

He had never been abroad before.

However, many grammarians do maintain that this analysis is imperfect.

If we accept that prepositions need a following noun group, before is readily classed as a preposition in the first sentence here and as an adverb in the second (compare he went abroad later).

However, this isn't a complete explanation either. In

The ship hove to.

The 'to' is obviously not a preposition - but it cannot be dropped from the sentence without leaving an ungrammatical residue. This is different from the above example using an adverb:

He had never been abroad before.

=> He had never been abroad. (OK)

In such cases, an analysis I subscribe to is that the 'heave to' construction cannot be separated into different parts - it's a multi-word lexeme (cf 'ship of the desert' for camel). If the 'to' in such a structure needs an individual name, the one it usually ends up with is 'particle', or, to show its affiliations, 'adverbial particle'.

I'd argue that 'bring to' and 'fall to' in Shoe's examples are multi-word lexemes.

A drop of whiskey brought him to. *A drop of whiskey brought him.

Fall to! DM:Fall!

Examples of to as a true adverb don't seem very common - but he may have found one in 'She pushed the door to.' But perhaps this is better analysed yet another way, as a directional / locative particle: 'I think she pushed the bolt to/home. Is it home?'

Apparently, a nautical expression uses 'to' as meaning 'into the wind', so this is (arguably! - how cohesive are turn and to here?) an adverbial usage:

We turned to and flew as much canvas as we could manage... (Google)