Hello @5304Pants ,
Welcome to the forum!
You can use this guide to migrate your node: How do I migrate my node to a new device? - Storj Docs
Just try 
You can move your identity from the SD card to the disk and use this path in your docker run command, since the identity without data is useless and vice versa - the data without identity is useless too. So, if your disk would die, you will be forced to start from scratch anyway, so the backup would not help either.
Use only ext4 filesystem if you do not want to troubleshoot different issues.
Use an extension card for the HDD, not external HDD if possible. If it’s not possible - make sure that your external HDD have enough power supply (it must be external).
Don’t ignore cooling, don’t cover too much of the Pi, use a fan or a box for Pi with a fan.