What would you do in my situation?

This is part needing career advice and part venting. Earlier this year, I took on an in-house remote graphic design position for a startup. It’s contract through a staffing agency and W-2. It was advertised as 30–40 hours a week and exactly my level of expertise. The first couple of months were as promised 30–40 hours a week, but then things took a dramatic shift. The hours cut down to as low as 3 hours one week during the third month, and haven’t been above 15 hours for all of the fourth and fifth month. They’ve told me to bear with them as they adjust through their growing pains, but there has been no update in months. Every week is completely unpredictable in terms of workflow. There was a two week period where my manager conveniently forgot to approve my timesheet so I wasn’t getting paid for two weeks. On top of that, my manager would ask me what I worked on to verify… while I’m over here feeling like I’m overworking and undercharging just to make this mess work. In terms of workflow, they’ve also given a part of the work that was initially my responsibility to the creative director, which I understand but again, zero communication. I’ve been trying to give them the benefit of the doubt but this is not sustainable as I’m not getting paid a living wage on some weeks and most importantly this is not what I agreed to. I’m sincerely wondering how you would handle this in my situation? While keeping dignity in tact and being aware of long term consequences. I feel hurt and disrespected. I’ve asked the recruiter for more info about when the hours might return, but she said they haven’t been updating her. I am on the verge of resigning and taking a temporary job at a coffeeshop until I find my next design position.