Hi Ashley,
There is not full documentation for the plugin, but it’s explained in most details on the left sidebar of this page (description tab).
As for setting values to 0, please note that 0 means to disable any control on that field, since you can’t (or at least, shouldn’t) have quantity of 0 for a product, if you can give me more details about what you’re trying to get, I will be glad to offer help.
As for #3, you need to enable the section you want to configure (min, max, step, etc..) and then enable the tick “Per product” on that tab, then you will see new fields in the product backend.
Hope this helps.
Omar