I think that I was able to beat the octopus the first time switching form with mouse singing. it's kind of fun in the fever of battle switching out quickly like that, and the octopus is really hard, you just have to plow through it with lots of food. it will take a slice out of you. stock up your larder as much as you think is needed, try again and if it dosn't work out see if you need to stock up more. octopus prime is an optional boss but that is little consolation for completists.
from my experience with keyboard switching I didn't run into your particular bug, what vs. of Aquaria are you running? but with silverflagon experiencing it as well it possibly widespread?