How is it possible to perform ghusl with a fractured foot and a cast preventing water from reaching it? Is tayammum permissible in this case? And what are the ways to get rid of masturbation?

Masturbation is forbidden, and one must repent from it. Regarding ghusl (definition) for janabah (definition): wash as much of your body as you can without harming your leg, and wipe over the cast or splint placed on it. Tayammum (definition) is not sufficient unless both washing and wiping are impossible.