1) I am going to begin by attempting, bs'd, to answer question (b) since this is the beginning of the Sugya. I would like to show, bs'd, that it is very close to the simple explanation of Iyov 37:11 to say that Af Bri is the Mal'ach of rain.

a. First, let us look at the word "Af." This word occurs in other places as the name of a Mal'ach. See Rabeinu Bachye to Shemos 20:8 on the verse, "Remember the Shabbos day," who writes that the reason we do not say "v'Hu Rachum" on Shabbos night is because there are three Mal'achim -- "Mashchis," "Af," and "Cheimah" -- who do not have permission to damage on Shabbos. We learn from here that there is a Mal'ach called "Af."

b. Now to the word "Bri": We read in Devarim 28:12: "Hash-m will open for you his good treasure house, the Shamayim, to give the rain of the land at the right time." The Roke'ach writes there, in his commentary on the Torah, that this means that Hash-m gives permission to the Mal'ach "Af Bri" to open up for you plentiful rain. The Roke'ach adds that in the Gematria form of "Atbash," the word "Bri" is the same as "Geshem."

In the Gematria style of "Atbash", the letter Alef switches with Taf, Beis switches with Reish, and so on. In other words, the first letter in the Alef-Beis becomes the last letter, and the second letter becomes the second to last letter. According to this, the word "Bri" which is composed of Beis, Reish, and Yud, becomes Shin, Gimel, and Mem. With a slight change of the order, this becomes Geshem, so Bri according to the "Atbash" Gematria system is rain.

c. Now I did say that I was following the simple explanation of the verse in Iyov 37:11, so I will now show, bs'd, that the Gematria of "Atbash" is actually used by the verses in Tanach itself. See Yirmeyah 51:41, "How has Sheshach been captured!" Rashi writes that "Sheshach" is the same as "Bavel" in Gematria "Atbash," so it means, "How has Babylon been captured!"

See also Yirmeyah 51:1, "The dwellers of Lev Kamai." Rashi writes that in Gematria "Atbash," "Lev Kamai" is the same as "Kasdim" (the Chaldeans).

d. I argue, therefore, that since we see that there are verses whose simple meaning cannot be understood without using "Atbash," it follows that we are close to the Pshat if we say that "Af Bri" means the Mal'ach of the rain.

e. We can now continue in Iyov 37:11 and can translate it to mean, "The Mal'ach of the rain will be Matri'ach the clouds" -- Af Bri causes the clouds to come and yield their rain. The verse concludes, "The cloud will scatter its Or." See Iyov 36:32 and Rashi that "Or" means rain (based on Ta'anis 7b).

f. I hope that I have succeeded in suggesting that the simple meaning of Iyov 37:11 is very close to saying that Af Bri is the Mal'ach of rain.

2) Now I will try to explain Tosfos in Nidah 16b (DH Mal'ach) who says that the Sar Matar acts only with the permission of Ha'Kadosh Baruch Hu.

(By the way, the Roke'ach that I cited above also states this. The Roke'ach was a Rishon slightly later than Tosfos, and often follows Tosfos.)

The Pri Megadim (Mishbetzos Zahav, OC 114:9, which I think you referred to) writes that the difference between rain and other forces of nature is that concerning rain there is no Shali'ach at all responsible for causing it to fall. Instead, when Hash-m wants it to rain he makes the plenty flow through Af Bri. Other forces are different. There is a Shali'ach appointed to start off with, and this Shali'ach is under constant Hashgachah, and, without Hash-m, no one can live for one moment. But the Shali'ach does have the capability to do something as long as Hash-m does not stop it.

I think one may understand this matter a little more by considering the planets and the stars. Generally speaking, they continue on the way that they have operated since the world was created. Rain is different. It changes all the time. The Metzudos David on Iyov 37:11 expresses this succintly. Sometimes the sky is totally clear with no sign of any rain on the way. Then the Mal'ach will cause a heavy rain cloud to come and spread its rain on the land. We can have an appreciation of the fact that Hash-m has a much closer Hashgachah when it comes to rain.

3) Rashi does write "Ananim" but obviously the rain comes from the clouds and the way that the Sar brings down the rain is by moving the clouds.

4) It is true that we have not yet seen a reference in the Bavli or the Midrash to the Mal'ach of the rain, but I argue that since we have seen that it is almost an explicit verse in Iyov, we need not be too concerned that we do not find something in Chazal.

(By the way, the Metzudos David, that I cited above, does write: "Chazal said that the name of the Mal'ach appointed on the rain is Af Bri," so possibly there is a statement of Chazal that we are not aware of.)

May you be blessed with a Gezunter Winter, with lots of good rain at the right time!

Dovid Bloom