Should I accept stock or just quit the startup entirely?

I started working for a startup part-time for free a couple of months ago. They told me they wanted to bring on another co-founder to their team and I was a perfect fit. I’m a software engineer for my full-time job, so this is just a side project. I also have young children, so that takes a lot of time as well. I made these things clear from the start that I can’t work on this full-time and the other co-founders don’t either. I didn’t think it would be a problem. Ever since I started, they expect me to work after 8-9pm and whenever they want to meet with me— it’s also after 8-9pm. I’m exhausted and not functional that late and they always seem surprised when I say I’m exhausted. However, I always give in and meet/work when they want. I get all of my start-up work done during my regular work day when I have breaks and it’s working out for me. However, the founders are not flexible at all and after 8-9pm are the only times they’re available. Also, they expect me to work on the weekend. I have no childcare then and that’s just not a possibility, so they expect me to work after my kids are in bed on the weekend. Im able to get the work done during the week, but they make me feel guilty when I don’t put in extra time on my days off from my full-time job. I didn’t do any work this weekend (or Friday because it was a very busy workday) and I can tell they’re annoyed with me. My family and my job that I get paid for comes first and I’ve made this clear, but it doesn’t seem to penetrate. I’m not getting paid a penny for my work. I figured if I wasn’t getting paid, I could really just work on it as much as possible without stressing myself because I’m helping THEM out. They needed an engineer and it’s starting to feel like I’m getting taken advantage of since it’s a one-sided relationship. They told me they’re going to give me stock options soon, but I have a feeling it’s going to be an insult of an offer since they need me, not the other way around. Their current product works for what it is, but all of their clients want WAY more added, so there’s a lot to do. It’s pretty barebones right now and most of the clients don’t even use 80% of its functionality. So I guess I’m wondering what is the minimum I should ask for? And really, if I should even put up with this anymore? It’s giving me a lot of stress for no money. It is slightly profitable, but they don’t want any of us to get compensation at this point (which I understand). All of my older friends tell me I’m being used and I’m a pushover, which is probably true. I just want some opinions from people I don’t know lol. Also…. One of the clients asked for me to help them out on their individual product and the founders want me to not get paid for it and instead put 100% of what I get into the company. I feel like that’s not fair.