OK, I was able to get it out. After staring at it for an inordinate amount of time, I came to the conclusion that it couldn't be a press fit in the top of the slide, as access to get it out would have been too tough, making it a terrible design. I don't have one of the wrenches with two downward facing cylinders mounted on a round plane, but just to check if maybe it was threaded in, I hit one of the holes sideways with a small screwdriver in the hole at an angle, and sure enough, the two pieces rotated. So, it is a two part, threaded collar which holds the screw to the slide. The screw has an area almost at the end with a smaller ID. The collar clamps around this smaller ID holding it captive.
I have added a photo of the bottom end of the screw and the two collar pieces which go around it and thread into the slide. The larger OD on the screw is captured in a sort of floating coupling between the smaller ID of the collar and the bottom of the hole, allowing it to move up or down.
As for the rehab, I want to paint it and also re-oil it properly Frosty. I've read that they were designed for oil, not grease, like it was covered in. I am now able to throw the screw into the parts washer, clean everything off, etc.
Thank you.