I have over 80 alts, and my wife has many more than that, so tracking some basic info is very useful for us.
I have a personal plugin that allows me to create a CSV file with the followings columns:
The date and time are the timestamp for the last event for a character. This is valid even if the client shuts down with the black quit screen, but not if the client crashes.
It requires a lot of manual initialization at this time, e.g to set up server level Lua files with the server name for each server. I believe this info is now available in the output from a /loc command.
The code to create the CSV file is a bash script that requires a Cygwin install to provide grep, sed, sort, etc. I could probably rewrite this to use python3.
I don't have a way to distinguish between multiple subscriptions in the same account. If you don't know what this means, you probably have one subscription per account.
Unfortunately a lot of the info you would like to see can not be retrieved through the Lua API. Some of these could be captured by continuously monitoring messages in the chat channels usually displayed in the General chat tab. I currently do this some of this by logging the chat tabs and analyzing the logs outside the game.
BTW, I am RingTailCat from lotro-wiki.com