Following up on my post from earlier in the week - got my no-damage hard mode run! As it turns out the Churchmouse boss had a bugged pattern on solo hard mode, and it made it nearly impossible to avoid damage which is why I was struggling so much with it up till now!
I got a little lucky because I didn't have to fight the frog boss this run. It's not a super difficult fight but it's really tough to avoid taking any damage. The "stop moving" mechanics in particular are still a little too tight for how much you have to move across the screen, and good luck if you have any speed down items.
Rabbit and Steel good. Play it!!!