There is one more typo. The correct one is 出逢いによって一つの心が明るく芽吹き(の is unnecessary)希望となって形づくられるとしたら. If it's 芽吹きの, 芽吹き is a noun, but actually 芽吹き is the continuous usage of the -masu stem of the verb 芽吹く here, i.e., it's 出逢いによって一つの心が明るく芽吹き、希望となって形づくられるとしたら.
The author would intentionally use the hiragana version なにものか in the original text to add ambiguity to the word. Indeed, なにものか can be 何者か, but 者 is usually only used for "person/people", and there is another interpretation 何物か for "thing" or other than "person/people". なにものか actually refers to (大きな)自然 (or, 神, 天 or something like that), as in the next sentence, so the author would think 何者か is not so appropriate here.
As you can see in these examples, it's important to give the quotation as faithful as possible to the original text to get correct and useful answers, needless to say.