I don't see a lot of difference between the English and Japanese script, but it seems you're right about Dark Force making it to Earth and that's how Earth was destroyed. Peculiar, indeed.
Personally, I think that Phantasy Star II could be rewritten so that it doesn't contain Dark Force at all. Dark Force is actually the least interesting aspect of PSII. It's Mother Brain and the earthling rule that make it such a brilliant game and story.
Could you post a link to this translated script? I'd like to read it all, since I'm working on several stories involving PSII. Thanks!
P.S.S. TITANIA is a better character in Fire Emblem than Tanith! Mwa hahahaha....
Sorry, wouldn't know anything about those characters, so I'll take your word for it. Never played the game. I chose my name after the Phoenician goddess.