Is there a reward for a person who served and nursed a non-relative who died after a serious illness, having been financially supported by him, and is it permissible to give charity on his behalf, and is the deceased aware of the good deeds and charities offered to him?

This person's compassion, his help to you, and your service and nursing of him are among the righteous deeds for which you will be rewarded, Allah willing, provided that they are not accompanied by khalwa (private seclusion), touching, looking, removing the hijab, or any other forbidden acts in Islamic law. If any of these occur, then you are sinful and must repent. Giving charity on his behalf is permissible, and its reward will reach him, Allah willing. The deceased knows about the good deeds done on his behalf, and their reward is conveyed to him if Allah accepts it from him, as he will find its effect in an increase in his blessings or a reduction in his torment.