Check this post.
This is a 5 steps guide to set up an OpenVPN client with NordVPN in Luci. It is partly based on the tutorial you refer to.
I own the WRT32X and the VPN service does start at boot after following this guide.
Regarding the error that says the network device is not present, check /etc/config/network. Find the config paragraph related to the VPN interface you created. option proto should come first. If it is not listed first, move it to the first line. I had the same issue than yours, it did the trick for me.
Alternatively, you can delete the VPN interface you created and re-create it with the following command lines (as suggested in the NordVPN tutorial). Adapt it to your situation.
uci set network.nordvpntun=interface
uci set network.nordvpntun.proto='none'
uci set network.nordvpntun.ifname='tun0'
uci commit network
I use that same package with 2 policies similar to yours.
The difference is that my CIDR for the second policy is 192.168.1.0/24. Notice the "0" instead of the "1" before the forward slash. I don't know if it matters.
Otherwise, your policies are listed in the right order it seems.
For info, you don't necessarily have to allocate static IPs to the devices like you are doing in your first policy, you can single out devices by MAC addresses or even network interface. Check the readme from the package here. and head to the section about src_addr