How to get remote access to the DVR via USB modem?

Question

linux

There is a vpn server with a white ip, an ASUS RT-N14U router (padavan firmware) with a USB modem and a DVR. The router connects to the internet > connects to the VPN server. The VPN server (82.х.х.х) gives the internal address 192.168.0.100, port 27100 is open from the server to the client (i.e., you can connect to VPN client port 27100 through 82.х.х.х:27100). When instead of a router I connect to a VPN through a computer, then there is access to this computer from the Internet (I checked it on a vnc connection). When creating a VPN connection on the router and turning on dmz, there is no access to the DVR. Need advice on how to properly redirect traffic to the IP of the DVR. Unfortunately, there is no VPN client on the registrar itself.
IP addresses:
server external (white) IP 82.146.х.х
server internal IP 192.168.0.1
USB modem 192.168.1.1
router 192.168.2.1
router (connected VPN) 192.168.0.100
video recorder 192.168.2.20

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.0.1     128.0.0.0       UG    0      0        0 ppp5
default         192.168.1.1     0.0.0.0         UG    1      0        0 weth0
82.146.х.х      192.168.1.1     255.255.255.255 UGH   0      0        0 weth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
128.0.0.0       192.168.0.1     128.0.0.0       UG    0      0        0 ppp5
192.168.0.0     192.168.0.1     255.255.255.0   UG    0      0        0 ppp5
192.168.0.1     *               255.255.255.255 UH    0      0        0 ppp5
192.168.1.0     *               255.255.255.0   U     0      0        0 weth0
192.168.2.0     *               255.255.255.0   U     0      0        0 br0


Port Forwards List
----------------------------------------
Source             Proto  Port Range  Redirect to     Local port
ALL                TCP    80          192.168.2.20    27100      
ALL                !ICMP              192.168.2.20

Answer 1

Do you have traffic between subnets? Is it possible to connect to the registrar from an external server, or at least from an internal one? You also need to open ports in the router for the registrar, those that the latter uses. Make port forwarding.
Feels like you overdid it. Draw the structure of your network.

Answer 2

The registrar has a default gateway set to 192.168.2.1 - ?