8G is pretty slim for running HA. I think the recommended SD card size is much larger. For that matter, a RPi 3B+ is becoming marginal for running HA anyway. I know. I have one. I have to keep my HA implementation pretty lean for it to run reliably. But it most certainly can be done.
There are probably a number of things you can do to get this environment running, at least until you can update your hardware. First and foremost, copy any backup files off that SD card to some other safe location and delete them.
Then look at the size of the database file, home-assistant_v2.db. Chances are that thing is huge. Copy it somewhere if you think you’ll need it, then shut down HA and delete that file. HA will create a new one when it restarts. Follow this guide to minimize its size going forward.
Next, look at all your integrations and add-ons. For example, why Z2M and not just ZHA? Running on minimal hardware, you want to minimize the number of additional processes you’re asking it to run.
I think if you get to a clean, minimum HA base install you’ll find some of the other problems you listed will go away. Or at least be easier to troubleshoot. Good luck!