Count of historical ticket by month based upon an open and closed date

I am in need of assistance with coming up with a function to count a list of ticket from 1/1/2018 - Current. Some are closed and some are still open.

My Goal:
1. Count of tickets opened in that month. This was easily solved with a count if statement for greater than or equal to the 1st of the month but less than the start of the following month.
2. Count of tickets opened in that month. Easily solved for using the same count if statement as above but referencing the closure date.
3. Difference between open and closed, easily solved with Open minus closed.
4. Count of tickets that remained open for more than one month. This is where I need help.

Example:
If the ticket was open in January and closed in March I want it to count as open for all three months.