With regard to what is called “khatam shifa”, it is an innovation (bid‘ah). The Prophet (blessings and peace of Allah be upon him) said: “The worst of matters are those which are newly invented (in religion). Every newly invented matter is an innovation, every innovation is a going astray, and every going astray is in the Fire.” With regard to these soorahs and adhkaar (dhikrs) that are mentioned in the question, this is something for which there is no evidence (daleel), and it is not permissible to do these things for which there is no evidence in the Book of our Lord or the Sunnah of our Prophet (blessings and peace of Allah be upon him).
What is prescribed in our religion is to offer supplication (du‘aa’) for the sick person and to ask Allah to heal him and purify him. That will have the greatest impact in taking away the disease and bringing about rapid healing. It was narrated from Ibn ‘Abbaas (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said: “Whoever visits a sick person whose time (of death) has not yet come, and says to him seven times ‘As’al Allah al-‘Azeem Rabb al-‘Arsh al-‘Azeem an yashfeeyaka (I ask Allah the Almighty, Lord of the Mighty Throne, to heal you)’, Allah will heal him of that sickness.”
Narrated by Ahmad (2137), Abu Dawood (3106) and at-Tirmidhi (2083); classed as saheeh by al-Albaani.
So you should offer supplication (du‘aa’) for him in the wording mentioned in this hadeeth and other saheeh hadeeths.
The same applies to giving charity. There is no doubt that spending for the sake of Allah is something that brings good. It was narrated from Abu Hurayrah (may Allah be pleased with him) that the Prophet (blessings and peace of Allah be upon him) said: “There is no day on which people wake up, but two angels come down and one of them says: ‘O Allaah, give more to the one who spends,’ and the other says, ‘O Allaah, send destruction upon the one who withholds.’”
Narrated by al-Bukhaari (1442) and Muslim (1010).
So spend and give charity, and be optimistic about compensation from Allah, may He be glorified.
With regard to praying behind an innovator, Shaykh al-Islam [Ibn Taymiyah] said in Majmoo‘ al-Fataawa (23/355):
With regard to praying behind an innovator, this is a matter concerning which there is a difference of opinion and it is subject to further discussion. If you cannot find any other imam apart from him, such as in the case of Jumu‘ah prayer which is only held in one place, or Eid prayer, or prayers during Hajj behind the imam who is in charge of Hajj, these prayers are to be offered behind anyone, whether he is righteous or otherwise, according to the consensus of Ahl as-Sunnah wa’l-Jamaa‘ah. Rather the ones who refrain from offering these prayers behind the imams are the followers of innovations such as the Raafidis and others like them, who do not attend any Jumu‘ah prayer or prayer in congregation. If there is only one mosque in the village, then praying in congregation behind an immoral person is better than praying on one’s own at home, lest that lead to giving up prayer in congregation altogether. But if it is possible to pray behind someone other than the innovator, that is undoubtedly better and preferable. But if he prays behind him, there is a scholarly difference of opinion concerning his prayer. The view of ash-Shaafa‘i and Abu Haneefah is that his prayer is valid; however in the madhhabs of Maalik and Ahmad there is a dispute concerning this issue and it is subject to further discussion.
However this only applies to bid‘ah that is known to be contrary to the Qur’an and Sunnah, such as the innovations of the Raafidis, Jahamis and so on. People argue about many issue of religion in this country, and both parties to an argument may innovators, and both of them may be ignorant and misinterpreting things, so the refusal of one of them to pray behind the other is not better than if it is the other way round. But once the Sunnah is established and becomes known, and one person or group goes against it, this is the matter concerning which there is a difference of scholarly opinion. And Allah knows best. End quote.
In Fataawa al-Lajnah ad-Daa’imah (7/364) there is the following question:
Is it permissible to pray behind an imam who is an innovator?
The committee replied:
Whoever can find an imam who is not an innovator should pray behind him and not behind the innovator. Whoever cannot find anyone except this innovator should advise him in the hope that he will give up his innovation. If he does not accept that advice, and his innovation involves shirk, such as those who seek the help of the dead or call upon them instead of Allah, or offer sacrifices to them, then he (the one who offered advice) should not pray behind him because he is a kaafir and his prayer is invalid, and it is not right to appoint him as an imam. If his innovation does not make him a kaafir, such as uttering the intention out loud, his prayer is valid as is the prayer of those who pray behind him. End quote.
With regard to calling these people (da‘wah) and advising them, seek the help of Allah first and foremost, make your intention sincere and intend to guide them to the right path, and Allah will help you in that.
You should explain to them that they are going against the teachings of Islam, with evidence and proof, and demonstrate that the specious argument they follow is wrong; you should also refer to scholars concerning issues that you are uncertain about, so that their specious arguments will not affect you and they will not defeat you in argument, lest the ignorant think that their view is correct. And you should pay attention to being kind and gentle in all of that.
And Allah knows best.