Whenever my VPN Interface loses connection then the FW and route rules switch to 'unknown' interface.
I have to manually reset the rules to the correct interface (ex; lt2p-offsite).

Is there way to have have the FW and Route automatically setup the correct interface after loss of connectivity from peer?

Yep, create static binding(s) for the user.


https://wiki.mikrotik.com/wiki/Manual:I ... 2TP_Server

Static interfaces are added administratively if there is a need to reference the particular interface name (in firewall rules or elsewhere) created for the particular user.