That's really a difference of particles. ~는/은 is used for the topic. ~가/이 is used for the subject of the topic. In this sentence, you do not need a topic because it's so simple.
When you want to talk about your thoughts on something, you can use both. (I think) this food is really expensive -> 저는 (topic = according to me) 이 음식이 (subject = this food) 진짜 비싸요.
If you want to see 저는 and 제가 together (which would be a harder sentence), you'd have to talk about yourself. 저는 제가 그 남자보다 더 강한 것 같아요 -> It seems to me that I'm stronger than that guy.
No, not at all. Although I have to say I learned English 1st anf my Korean writing is beater haha. My English handwriting is basically all capital letters...
Punctuation marks are not common practice in Korean language. They are Western concept introduced to the language to ease the teaching of Korean to foreign learners.
Korean relies on final verb endings (conjugation) to determine the nature of a sentence e.g. in this case, + (스)ㅂ니까 already implies the sentence is a formal question. There is no real need for a "question mark".
My guess is
"Auntie" is a familiar form of addressing an elderly female acquaintance. This would be the equivalent of "아줌마". For an older female acquaintance, use "누나/언니" (= "sis").
"아주머니" is a more general, but polite form of addressing a non acquainted (or not so well acquainted) lady, akin to "Ms or Ma'am" in English.