Sounds to me like you have isolated the trouble to the switch. Get a replacement from the parts store and just plug it in before installing it to try it. That way you aren't having to tear apart the column and if it doesn't fix the issue just return the switch.
Agreed, common problem on B bodies, just that I'd double check the wiring on the new switch with the FSM wiring diagram before plugging it in, some of the aftermarket switches have terminal feeds in the wrong pin location, as they are for other applications at times, and it never fails that your application isn't one of them, I've had this happen on a few aftermarket turn signal switches, Mopar and GM... it's easy enough to move the wires in the plug end by depressing the tang that holds it in the plastic pin housing, removing it and swapping it out in the desired order
Mike
