That’s funny how memory usage is a worry for everybody. I just replied to a similar question there : High memory usage with nothing running - #9 by manifesto.
ps_mem.py can help you if you are not confortable with htop.
Checkout the few commands and explanations, it can help. But your case is different as you already use a lot of swap (RAM shortage past or present).
Actually looking at the htop command you have heavy fat application. If you close chrome and /usr/share/team… you’ll probably gain some memory. You do not have so much mem and not much to claim in buffer/cache/shared…