Does to Todoist support recurring tasks in any manner? If not then can it be used with a third party app / software?
Yes we support recurring tasks. If you click on the date box area, then Recurring Dates & More, you will see the list of available options.
You can type in the date box "everyday at 2pm" for example.
What about if I want to make it the 7th day of every month? Everything I've tried so far hasn't worked.
"every 7" should give you what you want.