Kaffarah fast

My friend fell asleep after 9am very tired and he missed zuhr,asr and maghrib as the days are short in winter in the uk he woke up at isha around half 6 he was fasting a kaffarah fast it was the 7th day he is concerned does him missing three prayers due to sleep mean he must restart the kaffarah again or no

keeping in mind he was not intentionally trying to miss salah he kept drifting in and out of sleep and felt tired and went back to bed he did make these prayers up must he restart the kafaarah all over again?

also if he forgetfully ( not accidently) swallowed a fingernail is the fast invalid ( note this is not based on certainty but doubt and waswasah and he felt sure he didnt swallow anything)