Michael Altfield:
First of all, is it always safe to delete the contents of /var/lib/tor?
No, it changes Tor entry guards likely which could be the intention of
an adversary.
We have documentation on entry guards here:
Does that documentation need any improvements?
And why did I read that one should delete their Tor State File when changing physical locations?
Same as above. You need to know a bit about Tor entry guards to see why.