Moved it to the gallon and it bubbled nicely most evening and settled into separated liquid and potato/flour stuff by the next morning.
It's been in the fridge since. I pulled it out a bit ago to stir (with plastic utensils only) together and let come to room temp...or at least not really really cold.
I'm going to measure out my 6.5 cups tonight and start my large batch of bread to rise in the fridge overnight. I'll feed the yeast starter and let it stay out overnight so ifthe bread is good and does its thing properly, we're ready to go next time.
It looks pretty opaque when stirred, and there isn't a 'sourdough' aroma to it at all.