Hi flashing-blinkenlights,
Python has an excellent ecosystem with a number of mature server-side web frameworks, a wide variety of libraries, and a lot of learning resources to boot.
Flask and Django are both great frameworks for producing web applications, but they have different strengths. Judging from your description of your project, you need a Python-based server-side web framework with an easy-to-use ORM, and for that reason, I would recommend that you look into Django as it's a "batteries-included" kind of framework. Also, it has a great admin tool built-in that makes it very easy to produce a UI for managing the database entities you create directly from within the browser.
In case you, at some time, would like to evolve your platform to be REST API-driven to some degree (e.g., for consumption by external parties), Django also has the "Django Rest Framework" plug-in, which provides all the tooling and documentation needed to produce well-behaving and secure REST APIs.
As for the choice of webserver running in a reverse proxy configuration, you can use Apache HTTPD for sure. Very popular these days is a rival webserver called "Nginx," which performs well and with a lot of momentum.
For quickly and easily getting a Django app running in production, I can recommend considering Heroku, at least in the beginning. It offers a path of very low resistance, and you don't need to worry about the reverse proxy config either.
I hope this helps, and good luck with your project. 🙂
Best, Thomas