Ok brother Hani, the answer to your question, you said;
"Narrated from Jaffar from his father (as), that he said: “Fasting of Ashoura is forgiveness of one year sin",
First of all Shia do not fast on the day of Ashura. Secondly the Shia Imams have said one thing and I will look up the source when I get a chance but this is what they said,
"A lot of things (narrations) will be connected to us, many things (narrations) will be linked to us and they will be put forward on our behalf or as they are from us but they will not be from us. In fact they will have nothing to do with us. They will be false, either fabricated or exaggerated, so be aware of this",
When the Imams were asked, "So what do we do? Or how do we know?", the Imams replied by saying;
"Use the Quran as your measurement scale. Bring them along the Quran. And if they are according to the Quran then, accept them. But if they contradict the Quran, if they go against the Quran then, throw them against the wall",
These were the words used, "if they contradict the Quran, if they go against the Quran then, THROW THOSE NARRATIONS AGAINST THE WALL".
For your information Shias don't fast or keep a fast during the day of Ashura. Because for fast you have to do Niyath and there has to be a Sehri and an Aftari. So they don't fast on the day of Ashura. I will answer all your questions and brotherly concerns one by one. I hope nobody, no one tries to derail this process.