Yeah, that message is because FreeNAS 9.2.0 offers the histogram feature that ZFS on linux doesn't offer. So you are limited to read-only mode. But, for someone that has no access to their data, read-only mode is much better than nothing.
Hate to break it to you, but the pros that can fix stuff like what your problem is are 4-figure people that take the money up front and do not guarantee any data. :P