In any case, since 2011 sshuttle has supported DNS interception via a divert socket, so although it might not work today I suspect it should be somewhat straightforward to fix. I haven't looked into this yet as my only use case for sshuttle involves running it on the end host itself (typically my laptop).
However the new project has the same issues with DNS over VPN on FreeBSD. I have personally corresponded with the current maintainer, etc., and since they build and test only on Linux, it's not something that ever got fixed.
If you read the original HOWTO/README from the original project, it details the issues and I can confirm that no amount of settings changes or workarounds will allow you to get DNS over the tunnel on FreeBSD.
The threads I have managed to find largely amount to "it doesn't work." Are you aware of anywhere the specific details of the issue are posted (debug logs from sshuttle, packet captures, etc.)?