jio double nat

hi,am using 4g lte Jiofi 2 modem router usb tethered with Asus RT-ac68U running Asuswrt-Merlin 384.5 to connect to WAN, there are two problems am faced with connecting my cctv DVR to WAN 1.since the 4g modem doesn't have Bridge mode or dmz i cant get direct wan ip into Asus router,it has a DHCP...