Gilbasolutions

There are a few places you can check out for Australia. The Soil Sciecne Society of Australia has a pretty nice website https://www.soilscienceaustralia.org.au/ and https://www.soilscienceaustralia.org.au/about/about-soil/soils-data-maps-and-information-sources/ These are also useful:

Digital map imaging https://www.tern.org.au/news/news-australian-soil-classification-map/

This is really detailed for NSW https://espade.environment.nsw.gov.au/

id say yes. Thats either a standalone pigment application (perfectly safe) or a fungicide plus pigment application (Envu/Bayer Stressgard) which is also safe once it dries. The pigment is just copper based

Im assuming you took a handful of soil and threw it into the jar and allowed it to settle? The soil particles will then settle so coarse material at the bottom then silt then clay. Im guessing the dark grey layer is orgnaic matter but as I dont know what exactly you did and to what soil it is difficult to say conclusively.

are you legally allowed to use pendimethalin there?

If he used a resdual pre emergent herbicide how long it lasts is going to depend on what chemical it was. In the interim if you put some activated charcoal it will reduce its longevity and allow you you to reseed in a shorter timeframe.