"Took me twice as long to list a book & I can't seem to get the font size below 14 (I usually use 12)."

Do you have a template saved? I had a really old one and that imported OK into Sell Similar (Custom Template). Do you have an active listing that you like? I believe you can save this to Inventory and maybe use it to Sell Similar? (Only guessing). It may have your preferred font size.

Works OK with Firefox for me.