I was abt to send you a whole bible explaining what happens but.. I find it on my own and it felt.. I dont have the words.. Do the same, you will enjoy it even more than just some person explaining to you.
(Play Rune's route my favorite.) and for the endings ill explain...
just always hang with the one you want to route, always always. There would be a few times you need to separate but try to be with him as much as you could (with the options to hang with em. )