Is all the merit of charity mentioned in the message authentic? And is it permissible to act upon weak hadiths in this matter?

The majority of scholars permit acting upon a weak hadith concerning virtues, provided certain conditions are met. What is stated in the message is generally correct, except that some of what is mentioned therein warrants consideration:

Firstly: The phrase "The deceased did not mention charity except for the immense impact he witnessed after his death" is incorrect. The verse speaks of someone on their deathbed, not someone already deceased. Its apparent meaning is that he saw signs of his shortcomings, not the virtue of charity. It is also possible that charity was specifically mentioned in the verse for another reason.

Secondly: The phrase "Charity is the best of righteous deeds" is questionable. It could be rephrased as "Charity is among the best of righteous deeds."

Thirdly: The sentence "It closes seventy doors of evil in this world" is based on a weak hadith that is not authentic.

Fourthly: The statement "Charity prevents burning and drowning" is mentioned in a hadith with a severely flawed chain of narration and is not authentic.