I would prefer to use the version than can call on ImgBurn rather than DVDDecrypter, since ImgBurn is the vastly improved and updated burning engine from DVDDecrypter, but if you are happy with the setup, go ahead.
Have you updated DVDFab? The newest versions should be able to decrypt any dvds out there at the moment. The free section, DVDFab HD Decrypter should work for most dvds, except for the very latest releases with added protection.
Shrink is almost certainly having problems because the structural protections are not being removed properly and it cannot work with the files.
Another good program for removing encryption is AnyDVD. It works in the background to remove encryption, but also has a built in ripper if you want to use it. AnyDVD has no capability for compressing dvd-video by itself, but can be used in conjunction with DVDShrink for most dvds. If you run into one that causes problems for that combination, you can rip the entire disk to the hard drive with AnyDVD, then work with it using Shrink.
AnyDVD is not a free program, but there is a trial available for download.