Too much yeast in my poolish

Hello :)

I found some old frozen fresh yeast in my freezer yesterday, and thought I'd give it a go and see if it's still good.

The fresh yeast were frozen within the first few days of purchase, exactly two years ago today. It was the only time I baked with fresh yeast. The rest of the yeast has been frozen since then - not in an airtight container, not wrapped in cling film, it was dehydrated and covered in frost, definitely looked freezer burnt when I found them - Basically I didn't know what I was doing, and it has been moved from one fridge to another, to another over the years. 

I took out some and let them thaw in the fridge over night. This morning, when I took it out, it was properly thawed into a goo but still smell like yeast!  Not having a high hope, I mixed it with 200ml of luke warm water (about 35 °C)  and sprinkle two pinch of sugar into the mixture. 20 minutes past, nothing happened. About 30-40 minutes later, just before I planned to pour the mixture down the sink, I saw some bubbling. I then sprinkled another pinch of sugar, and it produced a small fizz. Still a bit doubtful, I proceed to stir the mixture. To my surprise, it produced a nice layer of foam.

Still somewhat doubtful, I mixed in 200g of flour and let it sit at the counter. About 1.5hr later, the poolish was happily bubbling and almost doubled (maybe 80%) in size. Now it does look like the yeast is definitely alive. It's also a good 28g of yeast goo to begin with. I've read that when using frozen fresh yeast, I may need to double the amount I use. All things considered, I think I might have used way way way too much yeast. Not knowing if the poolish is over-active, I have since put it back into the fridge hoping to slow down the process. 

I've spent the last few hours looking for help and suggestions but i'm totally lost. Now that I have a poolish with 200g flour, 200g water and 28g old yeast!

• What can I do to make sure I don't over-ferment the poolish? 
• How to store the poolish? Is it possible to split it into a few smaller batches of poolish and "feed" them with a bit more flour? Not sure "feed" is the right word since it's not a sourdough starter.

Given yeast is very difficult to source these day, and I'm running super low in supply, I would hate seeing them end up in the bin after surviving what seems like an impossible journey.

Thanks,

Andrea