How many regular pins / video / story pins should I create a month? How many iterations of pins per original piece of content (URL) should I create? What’s the best workflow on a monthly basis to achieve results?

I always recommend starting at 5 fresh pins per day, 80% of which should be image pins and the rest can be video pins. For idea pins, Pinterest recommends 1 per week, but obviously if you can manage more thats also okay. 
When it comes to iterations for the same URL, you really can create unlimited ones as long as you use new images. Some of our students create 3-5 new pins a day and some even do 20-30 pins a day. I would recommend you switch up images/descriptions using the Pin tracker (linked in Bonus section) and see what is a manageable workflow for you. 
This is why I recommend starting at 5 pins/day, so thats around 35 pins/week and then slowly moving up (if you see traction on your content). If you don’t see traction, you need to first fix your content/design strategy and then scale. 
It also helps to schedule your pins for the next 1-2 weeks in one go as it saves a lot of time and enables you to batch your marketing.