I hear his voice say "Okayyyyy....." when an AC is irrelevant haha

Another way to think about it, I'll use question 4 as the context. Let's say that question 4 instead said "All mice are fat." This statement would be asserting that every single mouse is fat (M→F). So to logically negate that we would say some mice are not fat (M←s→/F); or, one can be a mouse and not be fat (M and /F). The reason why "some" negates "all" is because with this (M←s→/F), we are saying that there is at least one mouse in the world who is not fat, or we could also be saying that all mice in the world are not fat. Since the range of "some" is 1-100, like you said, both statements could be true and both would negate the idea that every single mouse is fat.

I think where your confusion is coming from is forgetting to add the negation when you negate from "all" to "some". For example, to negate "All mice are fat (M→F)" with "Some mice are fat (M←s→F)" would be wrong. That is not properly negating the original M→F for exactly the reasons you said, it still leaves the possibility of 100. The correct negation would be "Some mice are not fat (M←s→/F)." This means that on the range from 0-100, that at least 1 mouse is not fat, and even if the other 99 are fat, that one mouse being not fat negates the claim that "All mice are fat." I hope that makes sense!