[Bumerang]

Having exactly the same background (system programming, linux, c/c++, python, never touched Javascript nor web development) I did the very same recently.

My solution was to use Django (DRF) for REST API and React for the front-end and Zurb Foundation as UI framework. Javascript is really easy to pick up and there are plenty of tools and tutorials available out there. Used Facebook JS SDK for FB login and sharing (because it's easy and ready to go, plus FB is popular enough to make the effort worth). I also used JWT for auth and session management, just to explore it and because it seemed simple enough for my purposes. Django will solve most of the security concerns for you.

In total, took me ~4 months while working full time to wrap my head around everything and build the website + deployment (Nginx, Fabric, Celery, supervisor... all the usual stuff).