Indeed. Forget about Liechtentstein. If it hadn't been for the oddity that it is a sovereign state nobody would go there. It is a boring place that just happens to have its own car licence plates.
As to how to get to Maienfeld: Forget about the overnight route via Salzburg. You will be completely knackered when you arrive. You'll be spending three hours seated on a bench in a station in the middle of the night when there is nothing open, nothing going on.
If you really want to do this overnight stay in the night train till Münich Ost, and get out there. So you would need a NJ ticket Venice - Munich Ost, and a normal ticket Munich Ost to Maienfeld. You arrival time would be the same. And you will be on one of the new NJ trains, so it should be reasonable sleep.
But I would still advise against it. Abandon the Idea that you can cover large distances to out of the way places in a trivial amount of time. Plan travel days as travel days. Leave Venice in the morning so you can do the trip in daylight, and actually enjoy it. Spend the night in Maienfeld if that means a lot to you (I can relate, have done things like that myself) and then continue to Aigle.
The 29,40 ticket for Maienfeld - Aigle assumes you have a Half Fare Card (a transport discount card). Depending on what your plans in Switzerland are this might be useful for you to get. Without it the ticket will be more expensive.