40k visitors per month isn't one per minute. It's anywhere from one per minute to 40k per second. Division of requests by time is the worst possible mistake in calculating load.
I have 200k visitors per month generating 8m page views and about 50m hits on the servers (with CDNs taking another few hundred million hits).
These all peak during the UK weekdays and wind down at nights and weekends.
Divisions over time aren't going to work, but neither is translating visitors into requests, especially as it's only the page views that have a beyond trivial computation cost.
Total Requests
Last Month
622,482> [...] before switching to Docker (even though I do love Docker).
This seems like a very drastic solution to problems he does not yet have. I've been responsible for similar thoughts before, but shortly after realized just how damn stupid I was.