You are causing yourself a world of hurt using the 'nvram migrate' process of setting up a new router. That has been obsolete for a very long time now (the script was abandoned).
That TM converted router is running RMerlin firmware illegally and, not as designed either. So any experience you may glean from it may or may not be relevant to your RT-AC68U, which
is supported.
There are so many things that have changed from 380.xx firmware to 384.xx firmware that using anything but the most basic settings (and even then; applied manually) is setting yourself up for random glitches now or in the future.
I would recommend you flash your router to the latest firmware, do a full reset to factory defaults (including formatting the JFFS partition) and then minimally and manually configure the router to secure it and connect to your ISP.
With a stable router above (if it isn't stable at this point, I would flash the router again with the latest firmware you want to use and do another full reset to factory defaults - it has helped many get their routers to a good/known state again), I would then suggest following the amtm Step-by-Step guide in the link in my signature below to clean install the latest scripts as needed.
It sounds like a lot of work, but I suspect that you've spent much more time already trying to achieve the same thing but not succeeding (and I would guess, never able to succeed either) with your current process.
See the link in my signature for further details to get your network and router up-to-date in as short a time as possible.
