Regarding the spindle pulley, it does sound like it may be pressed onto the spindle shaft, which could make it difficult to remove. You could try applying heat to the pulley to help loosen it or using a puller tool designed for removing pressed-on pulleys.
As for the X axis gib, it sounds like it may be too tight due to the broken gib strip. You could try using a file or sandpaper to smooth out any rough edges on the broken gib strip and see if that helps it move more smoothly. If not, you could try drilling and tapping a new screw, as you suggested, or looking for a replacement gib strip.