Three suggestions before lighting strategy:
1. Subject needs more distance from background. You want any shadows to fall out of frame. Think about it in terms of managing the light fall off (flash output) and angle of your key light too. Granted you used a door, but that was a limitation in choosing a blank flat background square to the camera as opposed to creating a neutral background by lighting for depth.
2. Camera height should be higher as others mention. If you think you were at eye level, look at the nose in your shots and notice you were shooting slightly upward. Start by holding the camera (focal plane) parallel to your subject, don't tilt the camera up, but raise your height and tilt the camera slightly downward. Your examples exaggerate the problem because the height is inconsistent and lack the uniformity desired. To keep it uniform, you need to be the same distance from each subject and adjust camera height each time. (When you change camera angle by tilting, you create the illusion of respective height for each person. Typically not good unless you want to make a short person seem taller). A tripod is best for keeping the same distance while adjusting height quickly.
3. No one has mentioned it, but I think your monitor is not adequate or calibrated well. If it was calibrated you would see the exposure and color issues with more confidence. Especially for portraits, color, brightness, contrast, saturation, tint are important to see accurately. Otherwise it becomes a guessing game and very difficult if not impossible to deliver portraits to clients. You can't control what monitor the client views images on, so yours needs to be standardized and accurate. A wide-gamut IPS monitor is best. You can calibrate other types of monitors, but will still have issues seeing details of highlights and shadows.