I was thinking about splitting the rest of it amongst several smaller jars and topping off with distilled water.
Is this a sound plan for storage? Would freezing (without glycol) kill the colony entirely? Would freezing be better or worse than leaving it at refrigerated temperature for months?
at that point you’re better off using a tablespoon or so of the slurry and making a starter. The yeast you pitch into your next batch will be much younger and more vital that way.
That slurry contains approximately 1.2 billion cells per milliliter; therefore, I would use roughly 40ml of slurry per gallon of wort in the 1.070 - 1.072 range.
I am just making a SWAG based on the color. The crop appears to be a mixture of break and yeast. I am being conservative by estimating that the the crop contains approximately 50% yeast cells (the percentage could be higher), which should be around 1.2 billion cells per milliliter. The only way to know for certain is to count. However, as I have mentioned before, yeast cultures are like nuclear weapons in that one does not need pin-point accuracy in order to get the job done. Two hundred milliliters of that stuff should fully attenuate 5 gallons of 1.072 wort without batting an eye. Heck, 150 milliliters should do the job.
S. cerevisiae - let’s say I started with a vial of yeast, how big of a single starter would it take to build-up the cell count for a batch this size (1.070)?
A 2L starter will provide a substantial margin of error for 5-gallons of 1.070 wort. However, a starter is a waste of time with that much yeast slurry at your disposal. All you need to do is to pitch 5 to 6 fluid ounces of that stuff.