You have to understand how deep learning works. Please start reading somewhere, maybe in Japanese, what happens in machine learning. DeepSpeech ist currently not yet an end user product. You won’t get results if you continue without any knowledge of what happens.
You are asking about high loss due to an UTF-8 error. You use a batch size of 4 for a single line. You set epochs to 5 for a single test run.
And again, 70 hours of input is not much, you won’t get results anywhere near what Google, … do.