Interactive Pricing Component with vanilla JS and SASS

I had quite a bit of trouble with the toggler on mobile view. I was able to persist the mobile layout design until ~370px, and then it just goes haywire. Should I lower the font-size, even though it doesn't seem like it is lowered in the design file? Is there something I'm missing in the design file to make the toggler design not fall apart?

Also, any general feedback would be greatly appreciated. Thank you!