Can I add another column in Fields Multiplier? How can I do that?

2. Can I add another column in Fields Multiplier? How can I do that?

It is not possible to add another column in the Fields Multiplier widget. If you want to have several columns, I would recommend the Configurable List widget instead. You can check out the widget here: https://widgets.jotform.com/widget/configurable_list 

You can also check out this guide on How to Set Up the Configurable List Widget.
Cheers.