For Change #4 some adjustments to the post body text were requested.

• Font size should be 18px
• Font weight should be 400
• Font color black on white background
• Values should be able to be changed in browser dev tools

In block style WordPress themes most of the CSS is in the theme.json file.

• The font size in a post is set in core WordPress to the CSS variable –wp–preset–font-size–normal. "normal" is set in WordPress itself to 16px, so I set "normal" in theme.json to 18px.
• I also increased the "small" font size from 16px to 18px. 
• Under "typography" I changed the font weight from 300 to 400.
• Also under "typography" the background was already set to white, so I left it.
• Yesterday I posted on how to view and change CSS variables in dev tools.  
• On my own, I also increased the size of "x-small" text from 14px to 16px, since the text in the sidebar and the footer seemed too small compared to the 18px post body text.

Once these changes are tested, they will become version 0.0.2 of the theme.