Thanks!

I actually thought of bleeding the system to let it loosen, but wasn't sure if that was the smartest thing to do, in case I end up having to get it to a shop. Even the one around the corner would be interesting without brakes.

When I tried bleeding it to loosen it, the fluid trickled out. But the caliper didn't loosen.

If that doesn't work, I assume next is removing the caliper and rotor as a unit?