This is one of the biggest things I think Lemmy needs. You should be able to create a backup of your profile and export/import it into another instance. That way if something happens or you have a problem with the instance admins you can migrate with no loss or minimal loss to your account.
I have done basically the same thing. With a few differences.
I setup Transmission and SaBnzbd on the NAS but offloaded sonarr/radar/prowlarr + jellyfin to my server so it’s not taking up resources from the NAS.
Found Usenet to download significantly faster overall and sonarr/radar get releases from them much quicker then torrents. Only about 1/15 downloads end up being torrents.
Also overseerr is an amazing tool that you should add into your system. I use it for myself but I also have made accounts for my family so instead of asking me to download something they can just press two buttons and it automatically does the rest.