Film industry is Melbourne isn't it? Could be wrong though.
Don't forget the weather can be prohibitive, ie, too hot to be on the beach all day; we've had to be in all day because it's 40 degrees today and have only just been out to play from 4 to 5.30.
Finding friends depends on how much you are willing to put in to it, you could make friends in any city if you put the effort in.
It is lonely at first even if you do know people, it all takes time and having a child is a good way to meet people so you are ahed in that respect
I don't know how much 600 quid would get you on a rental in Sydney, there must be a web site you can check it out on.
If your dp has an Australian passport, you can expect your application to be processed in under a month, providing everything else is in order, but remember that the Eastern States are oversubscribed in terms of migrants so it may take longer or you may be asked to settle elsewhere initially. And once you do get your PR visa you will have to make the move within 12 months.
It is a bloody long way and IME the best thing to do is mentally prepare for the break and don't mark time in terms of when you will be returning to Europe for a holiday, have the mindset that you are in Australia for the forseeable and any trip back is a treat.
Because your dp is a citizen, you will be eligilble to apply for benefits and child benefits initially, if you start to earn enough to take you over the threshold your benefits don't stop you just have to pay back the difference at the end of the financial year (june 30th)
IMO, freelancing in the film industry may have to go on hold while you establish yourselves, just speaking form experience, what I mean is don't get hung up on doing the dream job, that will come in time and emigrating is stressful enough anyway, unless you have super contacts already and can walk in to that kind of job
And as for you question will you get bored of Sydney after a month?..... I'd feel very sorry for you if you did!
welll that's all from me, hth