>and it’s important,
and (says)it’s important,
it 要件

>When it comes to making you a present
it 状況のit

>From my fifteenth yea
15歳の時以来
>I propose, therefore, to describe the experience of human loneliness exactly
as I have known it.
as 接続詞 exactly as I have known it. → describe
それゆえに僕は、自分が経験してきた、まさにそのままに人間の孤独体験を述べようと意図している。(行方訳)

>the others
他の物語
>those he liked
気に入った物語