I believe you need patience and time to teach voice recognition software to understand your voice. It sounds like that may not be the best solution for your father. Try a digital recorder with lots of GB storage. That way he can tell his stories and not have to think about anything else. That leaves you solving the problem of turning the story into text. I think you can get digital recorders that save as .mp3. If so, the next problem is to find a program that will convert that to text. The nearest I could find in a hurry is a free wave file to text converter.
I can't say how well the wave to text converter will work but the whole process after recording on the digital recorder will be free and if it doesn't work, a good digital recorder will allow you to slow the speech and pause to enable typing.
Unfortunately, due to the change in ownership of this web site and the lack of response by the owners to my requests to remove my email address from all administrative-level notifications and functionality, I have decided to remove my posts on AKFF. Thank you for the great times, the fantastic learning experiences and the many many fish. If you are desperate for the old content of this particular post, it is available below base64 encoded and bzip2 compressed.