I use "wii DVD Dumper" and it works quite well. As far as your file stopping at three hundred kb. It sounds like you are dumping to an sd card, in which case the the dump has to be split up in to parts. Make sure you are choosing to dump to your lan. If that is not the problem, then I would suggest using this dumper. File Details-Applications -
Note: You need the Custom IOS (IOS249) to use this application!