This app was mentioned in 4 comments, with an average of 1.25 upvotes
If you want to be able to make video calls(you can also turn off the video and just have audio), but without having to make an account, I suggest Jitsi Meet. It's a secure and encrypted way to talk to people. You can make a server with a password and send the link to whoever you want via email or etc. It's also available on Android devices. There's a few other alternatives as well with the same concept. No account required.
Another method is generating a new phone number for free. I used a few apps for this, but I prefer textPlus(android or apple). There's also Nextplus, which is pretty similar to it.
Lastly, if you can make a throwaway gmail account, you could use google hangouts(web, chrome extension, firefox extension, or android/mobile) for communication purposes.
You've given them time and understanding. You set down your boundaries and have a firm hold. You're taking care of yourself and not letting in that toxic. You have support from your friends.
You're doing it right. Good luck mate.
Jitsi Meet (20.2.3) https://play.google.com/store/apps/details?id=org.jitsi.meet
tl;dr I recommend Tox or Jami unless you're married to web-based and having a server (they're both serverless), otherwise use XMPP (keep reading).
The hate for XMPP is overblown, and it'll do what you want. Prosody is dirt simple to set up if you can install a package and edit a config file on your server.
Depending on exactly what you want in a web client, you've got a few options:
For native clients, you can stick to anything Jitsi (desktop, Android, iPhone) and have a consistent experience. Or if voice isn't important, use whatever you want.
You've got some other options, too.
More if you want it: Some friends of mine put together this comparison of messaging protocols/software.