Is it obligatory to make up for or offer expiation on behalf of a deceased father who suffered from psychosis/schizophrenia and did not fast? Is he considered accountable for performing these acts of worship? And what is the ruling on helping a father reduce smoking?

If the father is in a mental state where he does not comprehend his surroundings, then he is not accountable, nor is he required to make up for missed fasting, nor should others fast on his behalf, based on the hadith: "The pen has been lifted from three," and senility is added to them. However, if he is aware, then he is bound by religious obligations. If he intentionally neglects an obligation, it is not made up for him, and prayers for forgiveness should be made for him.

As for his prayer while sitting or with tayammum due to an excuse, there is no blame on him. However, if he is able to stand and perform ablution and does so, then his prayer is invalid.

Regarding helping him reduce smoking by giving him a smaller quantity, there is no sin upon you, as it is to alleviate evil and assist him in reducing the sin.

His good manners and forgiveness towards people are glad tidings, and good is hoped for him in that regard.

As for the transgressions he committed while he was aware, he has passed on to his Lord, and the prayer of a righteous child will benefit him, especially the prayer for forgiveness.