I know I will need to really save up to visit for sure first of all unless I win the lottery. I would like to visit both Brisbane and Sydney as I have some friends in both cities.

I would start my journey in DTW. How much time ideally should be between layovers especially between my last state side stop then onward to Australia?

How time is recommended when going from Australia back to states for the layovers also?

When is the best time of year to go as I do not tolerate high heat and humidity well?