It sounds like you want to quit… I’d still say it’s better to see it through, but I am not you and I’m not in your position and I don’t know all the details.
As for what you said, it doesn’t change it a ton… but it does sounds like they’re definitely being unrealistic and treating you unprofessionally. I think you have legitimate grievances. So, none of my advice should be interpreted as telling you not to advocate for yourself or stick up for yourself.
With more info, it sounds to me like you need to be clear and direct. If they are unable to talk on set, e-mail or a phone call during off hours seems to be your best bet. If you can get a friend or someone to act as your “manager” that’s even better - this is why actors pay agents and managers, so they can have someone be a hardass and stand up to directors and producers without having to be seen as a jerk themselves - they can just show up to set and be like “omg, yeah my agent is such a toughie, huh? oh, but thanks for getting lunch - I’m so excited!”
I don’t know who these people are, what their experience level is, or where you are, but no matter what, they shouldn’t be talking to you that way. You’re doing them a huge favor to work for them for free - the least they can do it make it as enjoyable as possible and not add to your stress or shift responsibilities on to you.
I would say this - pick the top three most important issues that you need solved. Call or e-mail whoever is at the top of the decision-making chain to solve those things. Tell them that you’re not enjoying your experience so far and that it’s not at all what you expected when you signed on and at this point you feel forced into a position where either things need to change or you feel like you may not be able to stay on-board. Then tell them 1, 2, and 3 that need to be solved. So, for example…
I need travel reimbursement - at least _____ dollars (maybe $5? or $10?) per day, because right now I’m losing a lot of money on this.
I need more accurate call times. If that’s not possible, please give me a standby time so I’m at home basically ready and then give me a phone call 30 minutes before I will be needed on set (or however long, depending on how far you travel - of course, then, you really need to be able to guarantee you can get there within that time and actually do it reliably).
I need a hard out-time each day. If I’m supplying my own lunches, snacks, water, etc. and I’m working for free, then I need to have a reasonable expectation of when I’ll be done and if we go over time, which I understand happens, then I need some kind of compensation for that, either in the form of money or a meal provided.
These are just examples, but I don’t think they’re unreasonable asks. Personally, I’d be asking for a lot more - things like snacks and meals provided by production, a daily pay rate, even if small, and a clarification that it is their job to talk to you about issues and it’s not your responsibility to “figure out” anything - whether that’s lunch, bathrooms, seating/holding areas, or whatever other problems it sounds like you have on that set.
Whatever you say, set a really clear and reasonable boundary, be a little flexible to their limitations, and be clear that if they don’t meet those expectations, then you’ll probably have to drop out of the project. I agree with Arthur’s points above, but everyone needs to have some kind of limit. The other side of that coin is that you don’t want to be seen as someone who lets others walk all over them either.
Best of luck!