'För' is a coordinating conjunction (like 'for' or 'because'), while 'för att' usually means 'in order to' or 'because'. In modern speech, they are often used interchangeably for 'because'.
No, 'men' is a coordinating conjunction. The word order remains Subject + Verb.
Both mean 'because', but 'för' is a coordinating conjunction (main clause order) and 'eftersom' is a subordinator (subordinate clause order).
In informal Swedish, yes. In formal writing, it is better to use 'Dessutom' or 'Härtill kommer...'.
Yes! But remember that the main clause that follows must have inversion. Example: Eftersom det regnar, stannar jag inne.
För is a coordinating conjunction (standard word order), while eftersom is a subjunction (BIFF rule). Eftersom is more common at the start of sentences.