I just want the text content to show in paragraphs, exactly as it is entered.
All manner of mucking around with the CSS simply has no effect - the text is just one block of text, no paragraphs.
Also, font size changes as you change the size of the containment box - how do you stop this happening? I just want to set font size and then set the area the text will appear in.
To break text into multiple lines you will have to use br tags (adding <br> at the end of each line). Please note that the text layer animations will not work in this case. You could also use the word-wrap option for wide text layers that are reaching out of the canvas.But in case you are planning to add multiple large text blocks, I'd recommend to add them as separate layers. The positioning, formatting and transitions will be easier to set up that way.
The layers are following up on the size changes of their content box. You should do it the other way around, enter the text first and the box will adjust to the content you inserted.