For 1 you need to edit css: go to Assets/section-main-product.css, find the lines saying “max-width: 44rem;” and delete them or comment them out.
For 2 this is supported in theme customization: go into customization, navigate to a product page, click “Product information” on the left, then under “Desktop media width” select “Small”.
For 3 you need custom coding, Dawn doesn’t seem to support vertical images. Your desired look is from store Riley Ridge, which uses the Prestige theme (paid).
For 4 go to Assets/base.css, find the style for h1 and change the font-size to whatever you like. Note that this will affect all h1’s in the theme, so also collection title and so on. That’s probably good because the theme should be visually consistent. If you want to change only the product page, add an override to the css file mentioned above.
To change the complete layout of product page firstly please check the theme customization options. If the options are not available then the layout needs to be setup with custom code. Thus you need to seek help of a developer to setup at a reasonable cost.