It is overwhelming info there, but the best way is to eat it like an elephant, one bite at a time.
You are not a pain and I'm sorry for responding late but I'm not on here every day.
If you have a single extra thermometer, the best way is to calibrate it.
Here is an article written by
@aart that should be helpful.
For humidity, an easier technique than measuring humidity is to weigh the eggs. Not all eggs need the same humidity. For example, some are more porous than others and therefor lose moisture faster. However, all eggs (regardless of species) should lose approximately 13-14% of their initial weight through the incubation process. A cheap but repeatable pocket gram scale is accurate enough to be more effective than using a hygrometer.
https://poultrykeeper.com/incubation-brooding/egg-incubation-weight-loss/
For new accurate thermometers, there are 3 I have found that are usually accurate out of the box. I don't know if any are available there but here they are in order from my least favorite to my most favorite.
https://www.amazon.com/Brinsea-BGB-.../B0099Y9SUQ/ref=cm_cr_arp_d_bdcrb_top?ie=UTF8
https://www.thermoworks.com/rt301wa/
https://us.govee.com/products/wi-fi-temperature-humidity-sensor?currency=USD&variant=37592920686777&utm_medium=cpc&utm_source=google&utm_campaign=Google Shopping&gclid=Cj0KCQjwj7CZBhDHARIsAPPWv3cdxFi3NCmkcIf1FVcZrJy4JDfaWcNWfRFOUPqMLO-Usi546yxpJ-QaAmspEALw_wcB
The latter may be the most accurate and reports both temperature and humidity to your smartphone via bluetooth.
They may be available in AU via other sources but they are from Brinsea, Thermoworks and Govee.