for the parts that are stripped, are they threading into metal?
If so, have you taken say a soldering iron and heated up the screws first to see if the problem could have been related to threadlock? usually if I have a stubborn one I will do this to break the threadlock bond, even blue threadlock depending on the location and amount used can be a problem.
as others have suggested, slotting and removing via a screw driver is usually what is done unless an easy-out is available for the screw size.