Hello. I am a student who has been studying Japanese for 3 years in classes, and independently for 1 year. I would like to offer my thoughts on the lyrics of this song. Granted, without the kanji booklet there can be no absolute certainty on everything that's being said. But considering my experience I feel it would prudent to lend my own opinion as a sort of peer evaluation.
Perhaps my biggest critique of this as you are translating is that you are either mishearing subtle differences in the syllables or chopping them up into other words. For instance, you have written down what can be clearly heard as "deshou" as "te shou" and "naegi" as "nae ki". You also don't seem to have a firm grasp of Japanese particles, such as splicing the "wo" (pronounced "o") particle into other words rather than allowing it to stand on its own. These things are understandable if you are not familiar with the language or accustomed to hearing it's sounds, but I'm sure you can see how that would drastically mess up the meaning in the process of translating. Japanese sentences tend to function in a grammatically different way than what you have put here.
This kind of "by ear" guessing is also present in initial translations of Whereabouts of the Miracle, and is part of the reason why the translation was grossly innacurate for the longest time. Even if the lyrics can be correctly heard, the kanji can change the meaning quite a bit.
Just a few things.
Toki, as used here, is a suffix meaning "when". As in, "when [preceeding sentence]". An example is, "Kodomo toki" means "When I was a child".
--Perhaps it would be better to state what I can hear with certainty. My translations of the lines are rough but I strongly feel that the romaji I have stated is accurate. Anytime I put in _____ means it's something I can't hear correctly.
"Kono naegi _________ toki" (when this sapling __________)
"Watashi wa __________ ni otona deshou" (I'll probably be [something related to an adult perhaps])
"Ookiku takaku nobita toki" (When it's grown out large and tall)
"Watashi wa ikiteru deshou ka?" (Will I be alive?)
"Ikiteiru deshou ka?" (Will I be alive?)
"Takusan na ha wo tsuketa toki" (When it's grown many leaves)
"Sekai wa ______ ni kawatteru deshou" (The world will probably [something about changing])
"______ taiju ni natta toki" (When ______ has become a large tree)
"Tsumi ni yurusareru deshou ka?" (Will these sins be forgiven?)
"Yurusareru deshou ka?" (Will they be forgiven?)
"Sennen no jikan sae mo" (Even the span of a thousand years)
"Anata ni wa matataki deshou" (Is to you like the blink of an eye)
And I can't make out the last stanza.
I say this not to say that my translation is for certain the accurate one. I'm just saying that you have, what I think, are quite a lot of innacuracies with the romaji and it's messing with your translation. There are things I feel you missed. Takusan na, for example, is very common and the first thing that my mind jumped to when I heard the line it was in, as was toki, deshou, and kitto. It isn't simply a matter of searching words in the dictionary, it's about understanding the contexts of a sentence, the conjugation of both verbs and adjectives, and particles. If your translation doesn't seem grammatically correct or comprehensible and you have to muck around with it in English first, than odds are you have translated it incorrectly. Japanese is not a nonsense language that has to be puzzled through, and Mothy's lyrics in particular are almost never confusing when translated correctly (Unless the song clearly exists for the purpose of being confusing, like Madame Merry Go Round).
This isn't even going into the idioms and turns of phrase that Japanese people have which have drastically different meanings than what they literally sound like.
I'm saying this because inaccurate translations for this series have been frequent and unrelenting and I would hate for you all to fall in the same trap that it took 2 years for the wiki to crawl out of. I'm glad you guys are interested in Japanese and want to see for yourself what the songs mean but be considerate not only of how you might be propagating inaccurate information, but of how much time and effort it takes to actually learn this language. I can't speak for any of you but I have been at this for years and though my improvement is drastic I am still not 100% fluent.
And of course, nothing is set in stone until we have the actual kana for these lyrics in our hands. Perhaps yours will end up being the more correct one.
I apologize if this offends anyone. I feel that accepting critique from others is the best way to grow. Translating by ear is a very tricky business if you're not a native speaker. I also apologize for the length of this reply--it gives off the impression I'm going on a rant here but I would just like to be as thorough as possible so as to avoid misstating the point I'm trying to get across.