Can I exercise after dialysis, and will it help my health?

Carefully. Exercise is alway beneficial to one's health but with diabetes with risk is hypoglycemia and hypoglycemia can also occur with kidney failure and dialysis. The key is frequent glucose monitoring before, during, & after exercise. It may be best to exercise on the days you do not have dialysis but monitor frequently and also always carry something with you to treat or prevent hypoglycemia.
Yup. Go wild assuming you dont have blood pressure / dizziness issues - make sure your back to normal then exercise - thats your best shot at living short of a new kidney.