The first half of your translation should be right. I think you have a good understanding of that part of the sentence:
By the time the knights were lured out,
In the second half of the sentence, 半ば is modifying 付いている, which is the 10th definition on jisho here. So, whether they win or lose (勝負) was already half decided.
Without grammar analysis, close to my original interpretation in the comment, the fact that he is going to die due to the curse is more unacceptable than letting his friend know he is going to die and make them feel lament about him since he has been struggling to seek one who cursed him to die to the last.
That is to say, the defeat by him is more ...
この先も is a set phrase that refers to a long period of time from now ("also for the next years/months to come", "beyond this point, too", etc.). When you say この先も, この always refers to now or here, not a particular event. If you have a specific "this" (e.g., a long study session) in mind, don't use この先.
I think it means each chapter of the story is translated into a different language, because of:
So I think it would be something like 英語で『星の王子さま』の第1章を読み、ドイツ語で『星の王子さま』の第2章を読み...
"Atelier/workshop" is one of the possible meanings of こうぼう, but こうぼう has lots of other meanings unrelated to one another. See this link.
Japanese has lots of homophones (words with the same sound) for historical reasons, so if you put a single word in hiragana into Google Translate like that, it can only give you the meaning of a random word that ...