Wow that's awesome that you're already saving 70%! And going to 60% is still excellent.
Perhaps as a kind of compromise, you could find a way to move to the studio apartment and keep the savings rate around 65%, either by picking up some small extra income, cutting expenses elsewhere, or both? If you could do that, I think you should feel no qualms about making the move if it would bring you greater happiness. I personally think you shouldn't feel qualms at 60%, but maybe giving yourself an objective to find another 5% will give you extra motivation!
Oh, I'll throw in one other option -- when I lived with roommates, we had a housekeeper come in once a week to clean, do dishes, laundry, etc. It's not a choice I would have made on my own, but they wanted it so I went along gracefully. I'll say, it really did help eliminate some of the mess and bad feelings that could have arisen otherwise. I'm not sure it will completely compensate for unthoughtful or messy roommates, but it could be a lower-cost option than moving when splitting the cost among you, while preserving your sanity.
Best wishes in whatever you decide!