In addition, I dont know if you could throw a football, but I believe you could.Its the same motion as throwing a football. With your build (you are very in good shape and has plenty of power)you should start trying to clear without using the whole body. If your hitting technique (including grip, finger, contact point, position) is correct ,clearing baseline to baseline would be effortless. Then when your hitting technique is smooth, you add the kinetic chain ( from leg, throwing hip forward). Your stroke should be beautifully completed. Non racket arm is important, but let it go naturally. Otherwise, you will have one more thing to worry about. Focus on foot position and throwing hip forward then your left arm should be pulled naturally (like when we try to throw something as hard as we could , Chest will be opened, non dominant arm will be pulled back)