Spinning out so advice would be great

So a few things with work today,

1 I am currently the only person at my job who can do what I can do (Cinema Projection) as the other guy is very sick and probably won't be back. I will have to carry the brunt of this by taking on all of the shifts for this role so my anxiety has gone wild as there are clashes with other clients and time off. ( I am technically freelance with them so not on their pay roll) So my little part time job is becoming more full time.

2 I have book to go to a LARP event at the end of the month. I mentioned this to the manager a few weeks ago who said they won't be showing anything that weekend. Then 1 hour after I pay everything I get shifts added that are on the dates I am away. I don't feel like I can turn them down because I need money but also I am the only projectioniat at present.

3 I was talking to one of their bar staff about applying for the open position and sent an email to management recommending him. I got an email back me tioning that there is procedure and I am not allowed to talk to staff about this sort of thing as it's lobbying. A procedure I was not aware of.

4 a couple of hours later I got an email about breaks on shift. This one is a mess up on my end and I should know better. It's basically not going out to vape on shift or pop to the shop so I am in the wrong here.

I can't help but feel like they're going to fire me even though I am the only one. I am self employed and I think the force that as they may get tax breaks for staff on payroll Vs freelancers invoicing so I can just say I am unavailable. But they are myost regular client and I do t want to piss them off.

I became self employed not just for this job but to have control over my time and it has helped me mentally to have that freedom. Now I feel like I'm loosing all that for an employer who will drop me as soon as I have trained my replacement.

So now I feel sick, the back of my neck has felt off for weeks (super sensitive like all the nerves are firing off) and it's gotten worse. Should I say I can't work for them on those dates or swallow the financial loss and go in?