As Salam Alaykum.
Let me know the authenticity of Hadeeth in which Prophet SAW said "Reciting Darood on me is like Noor(light) on PUL SIRAT(a bridge) and whoever sent 80 Darood on me on Jumah(friday) his 80 years sins are forgiven" Reference by Imam Sakhawee.
Also what is exact difference between Darood and Salam on Prophet SAW.

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.

This Hadeeth is reported by Al-Azadi in “Adh-Dhuafaa’” and by Ad-Daaraqutni in “Al-Afraad”, and Shaykh Al-Albaani said about it: “It is very weak.” Moreover, Ibn Hajar also classified it as weak, as is reported from him by Al-Munaawi in “Faydh Al-Qadeer”.

As regards the meaning of Allaah’s Salat upon the Prophet it means praising him and mentioning him with the angels, while our Salat upon him means supplicating Allaah to praise him with the angels.

With regard to sending our Salaam upon him:

1.     It is to supplicate Allaah to make him safe from all vices and faults and to protect him and safeguard him.

2.     As-Salaam here is one of Allaah’s Names, i.e. may As-Salaam (Allaah) always keep you and take care of you.

3.     Or it is a supplication to Allaah to make us submit ourselves to his [Prophet’s] legislation and abide by him [by following his guidance and example].

Al-Aloosi mentioned these three meanings while stating that the first meaning is the most preponderant one. For more benefit, please refer to Fatwa 120637.

Allaah Knows best.