Hi
1. When you editing the product, you can see the “Additional Details” field, such as the screenshot https://www.dropbox.com/s/k3hkq997u234fp5/Screenshot%202019-06-27%2007.19.17.png?dl=0
Just add your own new detail items as the following format:
key: ....
tempo: ....
For removing the default items, just leave those fields empty, they will not be displayed.
2 and 3, unfortunately, there’s no option for that, you have to customize the theme files. Our theme support only includes bug fixing, small adjustment, trouble using issues, don’t include the customization service, hope you understand.
Thanks