I'm sorry I can't really help you right now.
But you should try this translator:
http://excite.co.jp/world/english/

In the middle there's the option 英→日 and 日→英.
Select the second one (日→英) and copy only language constants text one by one and then copy 'n paste the results manually into the file. Don't copy the whole file at once 'cause it might corrupt and mess up the file.

So to save you some work, you can download the lastest Wordbook off Dev's website and complete the missing constants.