Port Forwarding For Home Based VPN Server

> [...] I'm unsure what to do with regard to the dynamic IP address of
> the VPN Server as this a home network and the machine's IP Address will
> change every time it's shut down and/or rebooted.  I know there is a way
> to handle this as part of the port forwarding but as I said I'm a little
> unclear on the process. [...]

   ADVANCED > Setup > LAN Setup : Address Reservation

   It's not really "part of the port forwarding", but, as you've
noticed, the target/server IP address appears in your port-forwarding
rule, so that server must have a fixed address.  Address reservation
tells the router's DHCP server to give that server the same IP address
every time it asks.  (The other way would be to assign a static address
to the server (and not use DHCP for it), but using a reserved (dynamic)
address lets you leave the server IP configuration on "automatic", and
let the router ensure that it always gets the desired address.)

   Either way, it's generally safer to shrink the DHCP address pool
(Starting IP Address, Ending IP Address) from the default of ".2" -
".254" (every available address) to something less, like, say, ".2" -
".199"), and then use the ".200" - .254" range for your reserved or
static addresses.  That way you can be sure that (no matter how stupid
it might be) the DHCP server won't accidentally issue any reserved or
static address to some other device.