How can I adjust text size and font in Debut Theme checkout screens?

Good morning. In my Debut Theme, I have increased my site headings and body a bit larger than default and use Helvetica bold. However, as I set up my checkout process, I realized the majority of the text in the information, shipping, and payment steps is small. I browsed the theme settings and other various areas but could not find a change that affected this text. I have attached a file showing each of the three screens for the checkout process as they currently display with the default text. I am a visually impaired access technology user. I can see the text in all other areas of my site very well but can’t see these three screens well. so I want to ensure accessibility for low vision users like myself. Is there code or changes I can make to CSS or other areas to make the text on these screens Helvetica Bold and adjust the text size?

www.theburpboss.com

password: leistu

Anyone have any ideas on this? Is this something that perhaps could be better managed with the one hour of support from experts?