Netgear C7000 / Nighthawk AC1900 Cable Modem Router combo

I have a new (yesterday) AC1900 Cable/WiFi combo router that I connected to my provider (Comcast) replacing an older device, which, in the previous configuration I had the cable modem connected to the WAN port on my ProSafe FVS336gV2 firewall. Works fine for internet access but...

In the FVS336 I had previously configured an IPSec VPN connecting to another unit at the office. And it all worked perfectly.

Now with the the new AC1900 connected to the internet and one network port on that connected to the WAN1 port on the FVS336 unit,  I do not appear to be able route traffic destined for the VPN from the LAN side of the AC1900's network.

AC1900 LAN - 192.168.1.1 routes to the Comcast IP for outbound traffic
ProSafe336 WAN - 192.168.1.2 routes to the default route 192.168.1.1
Prosafe336 LAN - 192.168.0.1
IPSec Network - 192.168.5.x

What I need to be able to do is to have traffic from the 192.168.0 and 192.168.1 route through the IPSec tunnel to the 192.168.5 network.

I can get the VPN up and can connect to the .5 netwrok but only from the 192.168.0 network (the LAN on the ProSafe336.

I can't find a way to create a static route on the AC1900 Cable unit. Seems like a feature that is on the regular AC1900 WiFi only device.

Is there a way to create static routes on the AC1900 Cable WiFi Combo device? I don't see that option in the menus.
Is this even possible? I need to have the VPN site to site for devices on the LAN segments of the FVS336 on either end.

Mike