The last three sentences are not quite accurate. It's not necessarily that nothing existed before the the big bang. It's a singularity event where mathematically we can simply not know what existed at/beforehand that moment. It is somewhat comparable with the event horizon of a black hole.
There is something happening/existing, otherwise a black hole would not be able to occupy space or affect light. We simply do not have the ability currently to understand what that is.
By definition, that is not nothing. It is a that we cannot know/understand it, at that moment. Notably, a lack of evidence is not evidence of nothing.
I grew up elsewhere but lived in Canberra (the capital in ACT) for about 4 years. I heard about all the scary, deadly things and was a bit worried also. Long-story, short - it's very unlikely to be an issue unless you live in certain areas.
The big funnel-web spiders are mainly an issue in an area north and a bit south of Sydney and reasonably close to the coast. I never saw one of them while living there (except in photos). My understanding also is that the spiders tend to live outside of the urban areas and more in the suburban/rural areas.
You're more likely to get into a car accident with a kangaroo than have an issue with those big-ass spiders, from what I was told. They're somewhat like deer in the US. But less of a joke because they are known to slash people with velociraptor-like foot naila/claws after being hit by cars and assumed to be dead by drivers who get out and check. Death by disoriented/injured kangaroo is scarier than death by spider in Australia for most, and I say this seriously!
The scariest spider stories I had... 1. out of town for several months and my bicycle had a black widow-looking (the redback, I believe) spider under the seat. and 2. one day, there was some sort of spiders born and sailing on the wind event where little spiders where everywhere (but they weren't the Sydney funnel-web or redback spiders, luckily).