how many endings there are?
Really only one, though, as the other is bad and makes that very apparent by being a bad/sad as well as short and just obviously the wrong choice and wrong ending lol. So really there is only one "true" ending, and it's pretty obvious when you reach this choice, but you should save it to make sure you choose the true one although the game does let you backtrack through the history to some degree.
This is a really wonderful game and story though and you should play it, at least try the demo! See my review below.