Hey Ian,
I spent some time a while ago looking at DiskCryptor (same version that you're dealing with). It's complicated by virtue of also having the capability of using keyfiles (which I was dealing with). I'm assuming you don't have any indication these were used. I ended up moving on to something else before I could spend more time on it, but I did write up a terrible python script that will try a wordlist against an encrypted image.
It's quick and dirty, but IIRC, I think it should try about 20-30 passwords a second. It's really slow. It is not a good solution, but since you're dealing with numerical candidates (hopefully!), it might help. You can always run it on multiple computers to speed things up.
I dug it up for you. It breaks easily, and could benefit hugely from a complete rewrite. Feel free to improve it! For now, it's something to start with. If you are dealing with keyfiles and you have found one, I also have a keyfile & password version of this script. Make sure you follow the instructions closely.
https://pastebin.com/D0rmkrbS
Hope it helps.
Like someone else mentioned, if you haven't already done so, contact your local law enforcement and/or a digital forensics company. They may be able to offer more assistance with a proper examination of your devices.