The one thing you are missing here is the keg is under positive pressure from within do it would be impossible for the oxygen to infiltrate while the CO2 is coming out.
I just added yeast to the fermenter and accidentally set temp to 30deg instead of 20deg. I have now backed it down to 20deg.
Question has this ruined the yeast?
I reckon another God way to work out efficiency is lots of recipes quote based on a % of efficiency.
Brew the exact recipe and see how close you are. I brewed one the other day that quoted 78% and I hit the exact OG. So that would mean GF getting 78%.
Yes or no
I have brewed several Ginger beers and my misses loves them.
I came in late in the conversation but did you add limes and lemons?
I have found blending the ginger and putting in a bag after boil easy.
Lots of sugar and yeast additive.