Haha, not sure why I'm being tagged here!
These are pretty standard questions which google will give you answers to, and you'll find that if you ask 10 people you'll get 10 different answers to, but I've been tagged so I'll give you a quick answer.
Breeding season won't change depending on which side of Melbourne you're on, but it'll change depending on how you cycle them and what locality you have, and to some extent between individuals. I used to breed Antaresia from the same lines as a friend, both of us in eastern Melbourne, and mine consistently went more than a month early every season. We never worked out why. Stimson's are usually about the latest of the Antaresia, ovulating anything from around now to around November or sometimes even a little later. Cool them down starting from something around April/May, cool hardest in June/July, start putting them together around June (earlier if you want) and keep pairing them up until either ovulation or until it's clear they're not going to breed that season. You can vary this considerably.
Weights/lengths and age are arguable, my views aren't typical. Most people will tell you to wait until they're 2.5 years old to pair them up, I generally do them a year earlier, although I grow mine much faster than I would recommend a newbie try to copy. I first bred Antaresia over 20 years ago but I've never weighed any of the ones I've bred. By the time they're old enough they should be comfortably large enough.
You can use a huge variety of feeding regimes. Basically, if they're overweight feed them less, if they're underweight (which is rare in adult captive snakes) feed them more, and if they're about right keep doing what you're doing. Smaller feeds more often or larger feeds less often or a mixture is up to you. For a newbie it's probably safest to keep feeds between about 10 and 20% of the snake's weight, I personally go substantially larger pretty routinely, but decades of experience tells me which snakes are and aren't going to do well with that at what times, and smaller feeds are generally a safer option.
Temperatures... you can go as complicated as you like, but basically, a hot end in the low 30s. 20-24 hours of heat in summmer down to about 8-14 hours of heat in winter depending on your local conditions (if your house stays warm at night in winter you'll need/want less time with the heat switched off). How low the temperatures get isn't too important as long as they're going to notice the difference. To some extent it depends on locality of the animals but generally it's no big deal.
Welcome to the hobby, I'm sure you'll love it