So reddit told me to just get a new carb. Given that, I figured I might as well see what I can do, since worst case is I'd still need a new carb. So I got a large drill bit, the largest one I could fit down in the hole. And I put a small vice grip on the end and started twisting it by hand. A little bit at a time, then put the seat back in and see how it closed. And little by little, it closed better and better. I didn't get it perfect, I didn't get it so the float closed perfectly horizontal, but it was pretty close and MUCH better than it was. It now moves inside the bowl, rather than the bowl pinching it down. So hopefully this actually works and the seal holds and it doesn't leak fuel through. We shall see.