Considerable works here. But it only means about the same as "good." You can say "great" or "excellent" to talk about larger progress.

Whom

Randomly put or random. "...except for randomly put far-off farmsteads and huts."

This is an excellent question and you're really close! It wouldn't be taken as sarcasm, but it is a lot nicer to say someone is being stupid rather than saying someone is stupid. Like you said with the word mad, it emphasizes he is only being mad at the moment, not that he is a mad person all the time. It sounds more natural to say "he is acting mad" than "he is being mad." But both are correct :)

"This" means you have the bird right in front of you. You might be holding it, it is close to you, or you are pointing to a picture of it. "It" refers to a bird that is not close to you or one you have never seen. A similar word is "that." You can point to a bird across the street and say "that bird is a good bird." (When sitting inside a car) "I like this car." (When standing outside a car) "I like that car."

I would have to watch the movie to really know for sure. But Johnny is a generic name and sometimes can be used to refer to anyone. G-string is a piece of revealing clothing, thought to be odd and distasteful. Simply put, Johnny G-string is an insult, especially if that guy has worn a g-string in the past.