Hi CT Viggen, I'm postulating you live in CT and are a Saab 9-3 Viggen owner or enthusiast? Those are fun cars, certainly ahead of their time!
I had a similar trajectory in that I was an itunes & ipod. When macbook hardware seemed to start slowing down with every os update, I reverted to installing other *nix distributions on it. Through this, I learned the User > Music > iTunes Music folder contains all the music files, so migrating my library out of macOS was pretty trivial.
To reconcile duplicates, I would recommend a current backup of your music library. Then use the option in iTunes > Library > 'Show Duplicate Items' from which you can review and remove:
https://www.howtogeek.com/409873/how-to-remove-duplicate-songs-from-itunes/I haven't personally used dbpoweramp but if it's providing the archiving you desire for your physical media, then I would check the settings to see if it can place its output in another folder to open up the option to use another framework.
I hope that helps with your primary concerns. You mention a couple other areas which have generated some synaptic pulses:
1) library is one your spouse's computer
2) itunes db is no longer valued
3) you have a FLAC library of your music
As my household has been telecommuting more, I decided to re-archive our music library into flac files rather than the lossy formats from years past. This put me on the hunt for something that could then stream to our various workspaces. I checked out Plex and some other options but then landed on JellyFin and haven't looked back:
https://jellyfin.org/This allows HTML5 streaming of most audio formats to just about any device in the house that can run a browser. This means we can access our library on the porch or in the garden from a phone or tablet and play it on headphones or a bluetooth speaker.
If you don't already have a HTPC like we did (built it nearly a decade ago), adding something like a NUC to your home network would allow streaming full quality while on wifi. A budget option for this is to setup a raspberryPi.
Depending on your data plan, you could even create a vpn to your home network to access this from anywhere, thus reducing the space needed on your phone (or keep the lossy files on your mobile and listen to the flac files when at home?).
If all of that seems like overkill, then take a look at your router and see if it supports plugging in an USB drive. This will allow similar access but your phone or tablet's media app will instead be accessing the files directly. When you want to add more media, simple archive it to the network attached drive.
Time to shovel some more snow, Happy Friday!