The dark exposures are from underexposing. You have to zero the meter when in manual mode. An ISO of 100 is too low for an indoor room no matter how bright it may look to you. And a shutter speed of 1/200th is too fast. A typical "bright" room may need an ISO of 800 or more and an aperture of 2.8 or larger to be able to use a shutter speed of 1/200th.