One final update!! Since I cleaned the eggs with hydrogen peroxide I had very few deaths. Batch number one had 4 remaining after cleaning, one died shortly before lockdown he didn't move much for a few days before. 3 goslings hatched but one had something wrong with him,possibly because I stupidly assisted him too early. Batch number two is hatching as we speak and I think maybe I threw one egg out since cleaning, which for that batch was pretty early on.
so I'd say the hydrogen peroxide cleaning was a total success, and saved these chicks. I only wish I had done it sooner! The first couple batches were far more fertile, my gander got lzy and the girls layed more during winter. I've been cleaning only dirty eggs for subsequent batches too. But unfortunately fewer are fertile. I'm all ready for a great hatch next year! I'd like to hatch enough goslings to sell some to pay for poultry feed throughout the year. Knowing what I know now, and with pete55s guide I think I can!