2. "Так" itself doesn't refer to the preceding sentence. "Так" can be omitted here. (Я как увидел, меня даже в дрожь бросило. - the meaning is the same; "так" is used here just to add some more emotion) "как" here is the synonym of "как только" = as soon as Я как увидел, ... = как только я увидел, ... = as soon as I saw...; the minute I saw...

1. "От пескарей" - one of forms of the word "пескари" (пескарь - gudgeon/minnow). It's a kind of fish, you can look for it in the Net. Also this fish is edible so the main character is frying them. The hole sentence can be translated as " There was smoke and stench in the room and only some embers remainded from minnows" 2. This sentence can be translated as " Mishka immediately reached for the groats to cook porridge. When I saw it, I was even trembled". So the phrase "как ... так" has 2 functions. The 1st one - connection with the previouse sentence, you're right. It explains that actions of the 2nd character are caused by actions of the 1st. The 2nd funct. is connecting of 2 predicates in the 2nd sentence: "увидел" and "в дрожь бросило". "Kaк" = "at that moment when...(smth happend)"

Как птица - like a bird

Don't learn Russian by this examples. It doesn't work!

(1) "Пескари" - "Пескарь" is species of fish: https://ru.wikipedia.org/wiki/Пескарь. "от пескарей одни угольки остались" - "only embers are left of the gudgeons". (2) "Я как увидел, так меня даже в дрожь бросило" - "The second I saw it, I even got chills". "Как ... так ..." means "at the same moment" here.