Font size too big throughout website? Help for visually-impaired creator!

Site URL: https://www.writingwithapurpose.net/

Hi there - I've just created a website in Squarespace and am on a big learning curve. I asked for feedback yesterday from a trusted friend who said my font size is "screaming" - way too big. My challenge is my vision, which is damaged from an autoimmune condition. For easy readability, I need to set font sizing for my reader not for me, lol. In Squarespace 7.1, what is the best font size to go with outside of headlines and titles. I'm using P1 a lot, which is likely my problem. Thank you in advance for input!!!  

You can permanently change the heading and paragraph text size in

In the Home Menu, click Design, then Site Styles, then (headings, paragraphs and so on), then change the heading sizes for all throughout your website

Also when you're typing, if you don't want double spacing, instead of continuing the words or pressing enter, hold down shift+enter and it will do a single break not double