Source for Various Customs

Hello Rabbi! I would appreciate it if the Rabbi could write to me the source for each custom I will list [about the Passover Seder]: 1. Some have the custom to carry the matzah wrapped in a cloth on their shoulders. 2. During "with blood and fire and pillars of smoke," some pour specifically with the index finger and not the pinky, and some believe with the ring finger. 3. Some have the custom to say before eating maror: "I am ready and prepared to fulfill the mitzvah of eating maror, etc.". 4. Some have the custom to say additional psalms related to the Grace After Meals after "Shir HaMa'alot." 5. Some have the custom to say before the Grace After Meals: "I am ready and prepared to fulfill the positive commandment of the Grace After Meals, etc.". 6. Some have the custom to say "Baruch Haba" when opening the door at "Shefoch Chamatcha."

Hello, 

I will write what I managed to find:

1. The custom of some Sephardic communities.   It seems to be based on the Rambam  (Chapter 7 of the Laws of Chametz and Matzah, Halacha 6) "In every generation, a person is obligated to show himself as if he himself has just now left the slavery of Egypt." Therefore, they made a demonstration and visualization of this.   and perhaps there is a slight hint to this in the book Kolbo (Siman 50)    and they lift the basket between their shoulders. 

2. The Rema ( Siman 473  Se'if 7)  wrote to throw with the "index finger,"  as it is said "this is the finger of God." 

And in Darkei Moshe, he brought that in the glosses to customs it is written to do with the "pinky," and this is not correct. 

And in Magen Avraham (there, Se'if Katan 28)  he brought in the name of the Yalkut (Parashat Va'era) that he brought from Pirkei de-Rabbi Eliezer, that with the ring finger the Holy One, blessed be He, struck the Egyptians. And he wrote that based on this, one should throw with the ring finger. 

3. The custom is based on the law explained in the Shulchan Aruch (Orach Chaim, Siman 60, Se'if 4) that mitzvot require intention. However,  additionally, the students of the Arizal wrote in his name, that every mitzvah should be fulfilled with action, speech, and thought, therefore before doing, one should say what mitzvah he is about to perform. [See Ben Ish Chai, Lech-Lecha, Ot 9. Derech Pikudecha, Introduction 3, and many others].

4. It is difficult to give general rules in this, according to what I have seen, there are psalms whose roots are from the Arizal, and part of the Yemenite customs, see Tiklal Shami. 

5. See number 3. 

6. Brought in Aruch HaShulchan, Siman 480, Se'if 1.