With my set up i don't really have a mold issue.
I get in there and stir it around and remove the worst ever so often. I rake the cleaner stuff over where i take the badly soiled parts out and just kind of rotate it as needed. With straw, the rain or garden hose can kind of wash the poo off the...
I can usually tell with mine at 4 to 5 weeks. Girls sometimes start finding their voices a lot sooner than drakes but I don't throw in the towel until they have no more baby peeps at all and either have a definite quack or rasp.
Can we see more photos of your entire setup? It's hard to make suggestions based soley on the one pool corner. 🙃
I use straw on the ground in my duck runs. It isn't a perfect solution but it's better than nothing.
Sadly there is no definitive yes or no answer.
With mine i have learned it's best to do the safety hole, then i wait and watch. Sometimes they do fine, but more often then not i end up having to assist. The linked article above is a good guideline to use. Ducks are slow to hatch so it's a fine...
That is the down side to having any animials. Where we live now i at least have my sis in law, we do chores for each other occasionally. But we both have a busy life and sometimes things come up when she isn't available or vice versa.
Unfortunately i have my first house sparrow show up to bother the Martins.
And now the Martins are fighting with the bluebirds that took up residence in the other Martin house. 🤨
They weren't doing that before this sparrow showed up. I think the sparrow started it.