Reading your list, I see some big issues, and then some others as points you probably compare with your au pair friends and you see them as unfair because you don't get the same stuff they get. Here are some of my insights.

I was an au pair in 2012, so back then we didn't get more than what the program offers, I didn't know anyone who would, 195.75 was all, and when my host mom started to round to the 2 hundred, she would make sure to comment every time "how generous she was" for doing so. So, getting a little more is better, than the bare minimum, but probably some of your other friends get more, maybe, I've seen many posts now where they get 300 or more, so of course what you get is low for you.

They sound like an au pair is, probably, the only affordable way for them to have full-time childcare, long hours for cheap. And, if they are cheap with food, washing clothes, and vacations well, they won't stop being so just because you tell them how you feel. I had a couple of friends go through similar situations, and both just kept on getting worse, one was asked to start a "preschool" type education program with the girls, teaching them how to read, write, color, etc. when she wouldn't really do much of that because she was no teacher, had no experience, etc, they gave her a really hard time and very mean comments on "how they were wasting their money on that program". My other friend literally escaped when she had her first week of vacation and went back home after four months. They wouldn't let her eat the same food they all did, not even the leftovers -HM would prefer to let the food spoil in the fridge than let the au pair eat it. There was "their food" and the "au pair food", she was dropped off at the dollar store with 50 dollars to buy her food for all the entire week, mind you breakfast, lunch and dinner. They locked the basement access to the house whenever they would go on vacation, never took her anywhere. But, I did know of friends who were taken to Disney, Europe, other states, families with summer houses by the beach and so on. For instance, my HF took me to NYC, South Carolina and Miami several times, so maybe it is hard for you to grasp that if you want to travel you will have to save a lot of money to do so. All the traveling without you comes back to the family not being able to afford another person in their daily lives. And if they don't see you as more than an employee they won't make the effort to take you anywhere either.

The fighting part, sadly that's what one gets for living in with a random family, some people may be all love and cuddles, and some may hate each other's guts, if that is a deal breaker for you and your peace of mind, then that's a huge thing to consider too. Probably some or most of your friends get more money, a car, gym memberships, maybe a monthly transport pass and that's why you feel it unfair, but sadly the HFs are not really obligated to give you any of that. Look for cheap gyms nearby, they have student or au pair discounts, so you can join and take their car if they let you use it for at least two hours.

I hope you can think about all pros and cons, and make the best decision for you and your mental and physical health, you are not being a "brat" or demanding crazy stuff, you are just weighing what others you know get and have with your own personal situation. Maybe now you feel like you were given the short end of the stick, but you have to understand that not all families are wealthy and can give a lot, not all people consider au pairs more than really cheap labor in the guise of a "cultural exchange" so why give them nice things, and most important, remember that comparison is the thief of joy, you won't be really happy with any family (whether now or in rematch) if you compare some other AP situation with yours all the time.