Taxonomies relations

I am currently working on my first WP site and struggeling with something. My websites should allow the admins nor moderators to upload tutoring videos related to series. I want that each series will be related to "lesson category".

For example, there will be a "Mathematics" category and under this category the moderators should be able to add series like "Linear Math - Fall", "Algebra - Winter", "Algebra - Fall" etc. In addition, I would like to link between a given series" and a given Tutor (which is basically a WP user).

I wondered, is there any way to make "Series" a child of "Category". So, when I add new series, it will be related to a given Category. Then, when creating a new post, i will choose a series and automatically, it will be connected to the correct category (which is the "parent" of the series taxonomy).

For now, I created two custom taxonomies called "Series" and "Lesson category" and for every new lesson post I mark its series and lesson category but it feels bad to me.

I am using the Toolset types plugin, if it conatins any of these features, it will be amazing.

So, my questions are:

1. How can I create "parenthood" relationship between two or more given taxonomies (series related to given category)?
2. How can I relate between a user and a taxonomy (user who is the tutor of a given series)?

Thanks, really appreciate your help!