WOW, a lot of very good advice. I do have a drill press but not a mill. I can send pics but I'm not very good at uploading the pics.
This is a very tired Colt, and it was used a lot. The screw is severely buggered. I've got time and am a patient person. I definitely don't want to do any further harm to it. I will continue to soak it and wait. The techniques you all mentioned at jarring the screw loose will come sometime down the road.