Great questions! OK here’s my 4 cents!
Scales, they can be tricky. My equivalent for 7 grams is 2 1/2 tsps. And there is a handy conversion tool on the web. You can increase the active yeast if you want to accommodate the lower ratio of active organisms or just use it as a straight substitution but know that it will take a little longer to bulk ferment.
Once you finish with the active dry yeast – make the change – it will be so much friendlier, especially for bread. No blooming and faster activation times. See picture from Modernist Bread – Techniques and Equipment.
Since you want to use up what you have, here is one suggestion for where to snag some water to bloom your yeast. I would hold back 40 g of the poolish water and use that to bloom your active yeast. And add that in during that phase of the mix. The 40 g assumes 4 loaf modern batch.
The bake quality above I do not think is due to the yeast. Often a gummy bottom is due to over proofing so the gluten is not strong enough to handle the oven spring and collapses on itself and/or you may not have developed the gluten fully in the mix. The loaf looks overproofed to me when you combine the undulating top and the gummy bottom. Easy to overproof these loaves which suggests that your yeast was certainly active enough!
I hope this helps!
Here is the picture and text from Modernist Bread.