Is there any proof from the authentic ahadith from the books of hadith supporting: 1) Imam standing by the chest (swadr) of the mayyit in janazah salaah and not (wast).

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We have not found any explicit Hadeeth stating that the Imaam should stand in the funeral prayer by the chest of the dead, but what is reported is that the Imaam stands by the head of a man [deceased male] and by the waist of a woman [deceased female]. Samurah ibn Jundub narrated that a woman died in labor and the Prophet performed the funeral prayer over her and he stood by her waist. [Al-Bukhari, Muslim and others]

Furthermore, it was reported that the coffin of a man was brought to Anas and he stood by the head of the coffin, and then the coffin of a woman was brought and he stood further down the coffin than that, and when he finished the funeral prayer, Al-‘Alaa’ ibn Ziyaad asked him: “O Abu Hamzah, did the Prophet stand where you stood when it was the funeral of a man and when it was the funeral of a woman like what we saw you doing?" He replied: “Yes.” He (the narrator) said: “Then, Al-‘Alaa’ ibn Ziyaad came to us and said: “Memorize this.” [Ahmad and others]

The scholars of the Hanbali School of jurisprudence who adopt the opinion that the Imaam should stand by the chest of the man, mentioned this Hadeeth where it says that he stands by his head, and they said that the two areas (of the body) are near to each other, so the one standing by the head is considered to be standing by the chest; Ibn Qudaamah said: “There is no difference of opinion in our School that the Sunnah is that the Imaam stands in the funeral prayer by the waist of the corpse of a woman and by the chest of the corpse of a man or at the level of his shoulders…..” Then he mentioned the Hadeeth of Anas and the Shaafi’i School giving it as evidence for standing by the head and then he said: “As regards the statement of those who say: the Imaam should stand by the head of a man, then this statement is not contradictory to the statement of those who say he should stand at the level of his chest because they (the two parts of the body) are near to each other; so the one who stands at one of them is considered to be standing at the other.”

Allaah Knows best.