So basically, you're saying the torso ball joint fits all the way into the socket as it is ? ...I've never heard of them being loose, they're made to be too tight by default, so that you may need to remove some material to make them fit, or best case they'll fit with enough strength... I'm not sure what to say, didn't even know it was possible for them to be loose.
I take it you are using the set of ball joints where the balls on both ends are the same size ? Neck ball joint has a larger and smaller ball, and the torso ball joint has 2 larger balls.
Other than that, super glue should be your best bet yes. I would try to not apply too much of it on the bottom of the socket, and more around the sides and top of it, and all around the ball itself.
Sorry for the issues, and glad to hear you still like it :)