@Tim_G I am currently learning web development as well so we can help each other on this new path.
I would totally recommend two resources to start Mozilla MDN web developer guide and Freecodecamp. Freecode camp being completely interactive and the Mozilla docs being mainly reading guides but both are quite good and as a plus for the Mozilla guide is that they include a Django tutorial as part of the server side tutorial.
Freecodecamp mainly focuses on teaching you Javascript so if you would like to use a python backend framework you should also take a python course. But if you don't mind its javascript focus it is pretty complete. It will freshen up your html and css, teach you javascript for the front end (currently vanilla javascript and jquery but the beta curriculum adds react as well ), https://d3js.org/ for data visualization and node/expressjs for the backend
This is their current front end path, they teach you the basics and then make you build stuff to really put to practice what you learn.

My end goal is to be able to intelligently write bits of software that are able to communicate and interact with APIs like REST API, to display and manipulate data on HTML5 pages.
If you only want to consume and interact with already made REST APIs you should focus and start on the frontend stuff. This will lead you straight to javascript first which is what you will use to interact with them from the browser.
I would advise you to first learn vanilla javascript (focusing on ES6+ if you can) and then think about learning and using libraries like reactjs or vuejs.