Recurring Monthly Tasks based upon Monthly Business Day

Hello, all.  
I'm trying to accomplish a few different things with Flow and Planner that I can't seem to figure out.  Sorry if there are existing posts to describe what I'm looking for.  I've been searching and it seems a lot of the results are outdated.  

1.  I need to create a group of monthly tasks that are assigned to a rotation of users (a new user each month.)  Is there a way for a user to enter their email and then assign a group of tasks to that user or some similar functionality I am missing?  
2. I need to assign dates to tasks on the Xth business day of a given month.  I have about 30 tasks that need to be done each month, but the exact calendar dates fluctuate per month based on business days (that is to say, having a recurring task for the 9th of each month would not suffice). My team is currently accomplishing this using an Excel spreadsheet, but we'd like to leverage Teams functionality if possible.  I found a template for a recurring flow that generates a Planner task with options for Daily, Weekly, Monthly, etc, but can't seem to get functionality beyond that.  Additionally, is there also a stock holiday calendar that can be drawn upon or created?  

Thanks in advance for any help.