Seems like a corner case, but if you are savvy with ssh, you can edit the /etc/config/network file manually, update the IP address there, and run /etc/init.d/network reload, and be back online without a reset.
VPN settings are tied to a specific Route10, yes. The settings will not be deleted unless you actually delete the device from the site. They will even persist through a factory reset of the device itself, so long as you do not delete it from the site. If you need help migrating to a different Route10, support can help migrate the settings, or if you use a local controller, the settings can be copied over in the raw database (services->vpn field).