At this point you don’t have many options ;-{
I would seal up the area with masking tape and news paper so the metal shavings don’t get down on to the logic board. Using a Dremel tool at a low RPM I would use a thin grinding wheel to cut a slot across the head of the screw.
'''But! Before I would even try turning the screws'''
I would heat up the screw as hot as I could get it without damaging the parts around. This would require first taking the masking tape and anything flammable away and then masking the area again with [https://www.uline.com/BL_6407/Kapton-Tape?keywords=polyimide+tape|Kapton tape] I would use focused heated air by using a small Precision Butane Torch then I would use a short quirt of freeze spray on the head to cool it so the screw would be shocked breaking the seal to the stud (thermal expansion and contraction).