It seems my partner's AppleMusic family plan has hijacked my payment options?

I recently joined on partner's AppleMusic family plan, and discovered today that all AppStore purchases need to go via his card. I have never added his card on my phone, and until joining on his AppleMusic, I used my own. Which, you know, was the one I had added. I can not add any other payment options, nor access my card via AppStore.

When I log in on Apple's webpages, I see that the only card listed there, is mine.

In Family Sharing (on the website), I see my partner listed as the organizer, and when I click my name, I'm instructed to go to Settings > Name > Family Sharing on my iPhone to change Family settings. However, on my iPhone, it says "Family information is not available".

Adding injury to insult, it seems that whenever my subscriptions need to be paid, they will be paid by my partner? Likely, this has already happened without us noticing.

As far as I know, I only agreed to be on his AppleMusic plan - I did *not* agree to transfer my purchasing power to him.

What in the Handmaid's Tale is this? And how do I fix it?