I was trying to get the knob off so I could potentially increase the amount of hot water getting mixed and it seemed to be coming off nicely but then snapped. By nicely, I mean it was a steady process; the thing was rusted/stuck on so bad I'm not sure it would have been possible to get off without breaking it.
I can turn the water on and off with pliers but that's not ideal obviously. Primarily I need some instruction on how to get this existing set up replaced with something new that has good hot water management. I see some screws but am not sure if I should do anything else without some guidance as to what it does (the ominous left only screw).