"I am good." has always been accepted. :)

착하다 is strictly about one's personality.

Sorry I do not know the difference in their meaning, but 1 thing i know: grammatical rules.

좋다 is a 'regular' word, while 착하다 is '하다' word.

So 좋다 becomes 좋아 and 좋습니다 etc

While 착하다 becomes 착해 and 착합니다 etc

I'm assuming 좋다 refers to positive likeability, and 착하다 refers to kindness

Me eiether

Same

Small is "작다".