The best way to get them off in my opinion is to use a air cutting wheel to cut a line in the top of each screw. You can use that slach cut like the head of a flathead screw.

You must put the TPS back on the throttle body before you adjust it. The way you adjust it is by checking the voltage from the sensor, and you rotate the sensor in the throttle body until you've got it reading the right voltage, and finally you tighten the TPS.

I would replace the 2 screws you cut with new ones of the same threads with an actual head on them. It makes for easier future adjustments.