It doesn't seem that you used amtm to do the above?
https://diversion.ch/amtm.html
I would recommend the following steps to get this working.
First, save any files you need off of the USB drive. Once done, from the GUI, Safely remove it.
At this point, I would also format the USB drive in a computer to ensure there will be no unwanted interactions when re-used in the router, below.
Next, save any files you are using or have created in the jffs partition. Including any OpenVPN (or other files) you need to re-use. If it is easier to re-create them (and if they are using just default settings, it is easier), save them 'just in case'.
Now, with the USB drive removed;
- Enable 'format jffs partition on next reboot' and make sure you hit the 'Apply' button on that page.
- Reboot the router 3 times in the next 15 minutes or so. Making sure to wait for 5 to 10 minutes between reboots.
- After the last reboot, wait at least 5 minutes to allow the router to settle (the CPU cores should be idle by then) and then SSH into the router and use the curl command to install amtm from the link above.
- Plug in the USB drive and be sure it is the only USB device plugged in.
- Using amtm, format the USB drive using 'fd' using Ext4 with journaling enabled.
- Make sure to create a label for the drive too.
- After the router has rebooted, SSH into the router, start amtm and create a swap file (I always use 2GB, max).
- Enable the disk checker in amtm for the drive. Use the command 'dc' in amtm to do so.
- Using amtm, enter '1' and this will begin the installer for Diversion.
- It will also install Entware (and optionally, pixelserv-tls, if selected).
At this point, you should have a properly formatted USB drive, a usable swap file, and amtm Diversion and Entware installed and all properly integrated.
After about an hour of the above working as expected, I would recommend you reboot the router and check the disk checker log (in amtm, 'dcl') to make sure there are no errors showing.
Now, you should be able to install available amtm scripts as needed, knowing that amtm, Entware, and the supported scripts will all work properly.