MacOS – How to make screenshots be true pixels

It is impossible to deliver an "answer" to this question. You are asking for something that is purely opinion-based. I have friends who use super small fonts and it's very comfortable for them. I also have friends who use larger fonts, and that works best for them. I personally use a variety of font sizes depending on what Mac I am on and what App I'm using. Your best best is to work with whatever font size suits you, despite what anybody else tells you.

There is no "one-size-fits-all" answer to your question.

Your trackpad is definitely dead. It needs a replacement. The dead line means that it is slowly dying. I have had these things. Probably your connector is getting old. But mine got burnt up because the hotel I was staying in did not have proper grounding in their mains supply. This meant that current was flowing from the metal parts and trackpad (it is electrified), through my body, and onto any grounded metal surface I touched. Trackpads are very sensitive to current changes as they have very thin wires running through them. The high ground current burns them off, either row by row or column by column.