Hi there, thank you for your kind words regarding the plugin, I’m really glad its adding value for you!
After searching for a solution to the tax issue we decided to write this for ourselves and then release it to see if there was a need for it and also to see how compatible it would be with other WooCommerce stores and plugins as such the plugin itself is still very new – we only released version 1.0.0 a month ago! So we are looking closely at feedback to see if it is being used and how we can improve it and we do have a few ideas for features we would like to add, some in the base plugin and some potentially in a premium format to help fund development of the plugin and as such, compatibility with shipping items and custom items is one of the features we are looking at.
With regard to the 404 error, thank you for alerting us, we have released an updated version of the plugin which includes the missing file and with that a nice little “extra” which allows for adding manual refunds as a partial amount of the inclusive tax price on line items.
Please do try it out and let us know how it goes!