I’d switch accounts sooner than later! Your backgrounds should be easy to switch over. But yes, unfortunately you’ll need to switch over to a new account if you don’t want to lose your progress. Remaking characters and outfits will of course be tedious, but it’s your best solution—unfortunately. As for backgrounds, you should be able to just right click all downloaded backgrounds/overlays from your portal to your computer, then upload into a new portal.
The entire thing is, again, tedious, but it ensures your stuff isn’t lost. I hope all goes well for you!