Try to update your Intel CPU driver. That may solve the problem even with hardware acceleration enabled. When hardware acceleration is enabled, BD3D2MK3D uses the DLL provided by Intel to decode the video. It is normally somewhat faster than the software DLL provided with BD3D2MK3D, but it is often unstable. It is therefore necessary to always check if you have the latest version.
CRF 0 is lossless, but you will obtain a very large file, most probably much bigger than the original AVC + MVC streams together. around 50 GB. IMO, it doesn't make sense to decrease the CRF value below 18. x264 is a much better h264 encoder than most other encoders, probably including the encoder that has been used to encode the original BD. It is therefore normal to obtain a small file size, especially if the movie is made of CGI graphics with very smooth and clean images, without much noise. Personally, I consider a final file size of 5GB as perfectly normal, but if you are really picky, try to decrease the CRF value. Decreasing the value by 3 means approximately doubling the size of the video stream, so try CRF 20 and you should obtain approximately a 8 GB MKV (with the audio stream).
Anyway, don't forget that the videos on BD are very big only (mostly) for commercial reasons. Trust your eyes and don't trust the guys who explain that you must use a certain bitrate for a good quality. It's pure nonsense, as I have already explained several times
elsewhere.