Horrible situation

[Ballroomdancing]

Company offers no support. No one is accountable. Setup doesn't work and tasks (I have no experience of) dumped on me because there is no one else . If I raise a concern nothing happens.

Unstable company and I am stressed out and feel ill. I have tried to distance myself but it doesn't work.

At risk of stating the obvious, it sounds like it is time to find a new role.

Time to polish up your CV and move on.
Pop into one or two agencies in your lunch break. Start making a job out of finding another job.
Good luck OP.

Start job hunting. If you can do that within the security of current job so much the better.

Had an interview in 4 days of immediate resignation/final straw/leaving a mistake of new job and today, an old ex employer has accepted my application to progress to next stage. A couple of agencies were willing to chat too.

I like to hope you can come back from bad job choices.