Is the Fidyah obligatory for a diabetic patient whom the doctor has forbidden from fasting and who takes insulin twice daily, and what is its amount, knowing that he follows the Maliki school of thought?

We ask Allah for your father's swift recovery. If a trusted doctor determines that he cannot fast now or in the future, then he is permitted not to fast, and he should feed a poor person for each day [he misses]. Insulin injections during the day do not affect the validity of the fast.