Most filesystems do not maintain a directory of where the hardlinks to a file (or more precisely, to an indode) are.

So you'll have to scan the whole filesystem to find all hardlinks. You can do this using
find -inum <inode number>

command should not contain multiple words. This is the cause of the [ error you see. You should set any flags separately.

Also, you should use pytivo_user to set the running uid, and not daemon -u. See the rc.subr(8) man page for all these magic variables.

Also, you should let the rc subsystem know that pytivo is a Python script so that it can find the process when it checks to see if it's running.

Finally, you should use the idiomatic set_rcvar for rcvar.

Something like this (I'm not sure this is the right Python path):

Beginners may find it difficult to relate the facts from the formal documentation on the BSD rc.d framework with the practical tasks of rc.d scripting. In this article, we consider a few typical cases of increasing complexity, show rc.d features suited for each case, and discuss how they work. Such an examination should provide reference points for further study of the design and efficient application of rc.d.